There are several species of clam belonging to the family Tridacnidae, which are best known as the tridacnids or giant clams. Of these, one of the most attractive species is Tridacna maxima, which is also one of the most commonly offered species available to hobbyists. I say most attractive because they can come in a wide range of colors, which can be arranged in a variety of unusual patterns, with many specimens being striped, sprinkled, spotted, blotched, marbled, etc. The colors themselves also range from black and white, with essentially everything else in between being seen on some specimen or another. In fact, I'd say it's harder to find a maxima that's unattractive than to find one that is.

Basic Information

To get started, maxima is the most widely distributed species of the tridacnids. They're found in the Red Sea and from East Africa all the way across the Indo-Pacific to Polynesia. They also live as far north as southern Japan, and as far south as the Great Barrier Reef (Rosewater 1965). Maximas can be found in high numbers around many reef areas where waters are relatively shallow and clear, with the majority living at depths less than about 25 feet. Some can be found living as deep as about 50 feet, but their abundance drops off dramatically below about 25 feet, with these deeper-living clams occurring mostly as solitary individuals (Jaubert 1977).

Maxima range

Regardless of their depth of occurrence, essentially all of them are found living on limestone substrates, on top of living corals, or on coral rubble. Supposedly they're occasionally found on sandy bottoms (Pasaribu 1988), but after doing a lot of diving around Japan and Indonesia I have yet to see this. Regardless, on hard bottoms maximas can chemically bore a shallow indentation into the substrate that the bottom of their shells fits into, and they strongly affix themselves in place using a tough structure called a byssus. So, they typically stay in one spot for life, with the bottom third or half of the shell kept out of sight in their burrow. Conversely, on coral rubble bottoms they simply bury themselves amongst the coral chunks and attach to something solid with their byssus if they can. Again, usually only part of the shell rises above the substrate. The odd thing is that they won't do this in aquariums, though. It seems that if they don't start making a burrow while they're relatively tiny, they won't do it at all. So, don't expect a specimen to dig into your live rock. Regardless, they almost always attach to the substrate using their byssus anyway.

Aside from that, the most notable thing to point out here is that, like all the other members of the family, maximas harbor large populations of zooxanthellae. These single-celled photosynthetic algae live in the tissues of a host clam primarily within a specialized system of tubes that permeate the fleshy, colorful, mantle tissue that extends from the top of the shell, and when given enough light, they can make far more food than they need for themselves. The extra food (in the form of carbon and energy-packed glucose) is then given to the clam host, which is the same thing that occurs within most reef-dwelling corals.

Under optimal conditions, these zooxanthellae are constantly multiplying within a tridacnid, and some of these live algal cells can be digested by specialized amoeboid cells within the host, too. So, a host clam can rely on its zooxanthellae for more than just sugar, and is considered to be a "farmer" to some degree since it can consume these surplus zooxanthellae grown inside its body.

In addition, all tridacnids can also absorb a variety of nutrients directly from seawater. Their fleshy mantle is covered by a specialized tissue that can very effectively take in dissolved nutrients like ammonia, nitrate, and phosphates. So, here they have a third means of nutrient acquisition, with one more to go.

The last way they cover their nutritional needs is through filter-feeding. All tridacnids can eat fine particulate matter strained from surrounding waters by their specialized gills, which not only work to exchange carbon dioxide and oxygen, but can also act as sieves that can collect such particles. A tridacnid, like most other clams, pumps water into its body chamber, where it flows over the finely-branched gills and then flows out the other end of the body chamber, minus some particulates. These collected bits are can include phytoplankton, zooplankton, and detritus, meaning they can make use of a broad range of things.

Identification

When it comes to identification, once you know what to look for maxima is usually pretty easy to distinguish from all other tridacnids with the exception of T. crocea. So, I'll go over the basic features used to ID them, and then give you some tips on how to differentiate them from croceas, too.

When it comes to shells, they're almost always grayish-white when clean. However, one of the interesting things about the shells of this species is that sometimes they may be tinted with light yellow or pinkish-orange. Rarely, the shell may also be completely yellow. It's almost always strongly elongated in form, being much longer than it is tall, and some maximas are very thin from side to side while others are quite fat. Deformed shells are not particularly uncommon either, as maximas sometimes live in very crowded groups and/or partially burrowed into coral rock preventing them from producing a normally-shaped shell. Regardless, at its top each half of the shell typically has four or five smoothly-curved and inter-digitating projections that are symmetrical to those on the other, allowing the them to close together tightly. However, there are occasional individuals that have more elongated and even pointed tooth-like projections that don't inter-digitate as smoothly with those on the opposite side.

Some species of tridacnids have petal or shelf-like structures on their shells, which are called scutes, and maxima is one of them. In fact, their shells are typically covered by numerous tightly-spaced but thin scutes, which run in rows from the bottom to the top of the shell. However, when maximas partially burrow into the substrate, many of these scutes are either not formed in the first place, or are broken/eroded away in the process. So, maxima shells oftentimes have no scutes on the bottom portion, while numerous scutes are still present on the rest. Still, there are occasional individuals that have none at all for some reason, while aquacultured specimens that are not permitted to burrow typically retain most or all of their scutes.

Also note that it's possible for a maxima's shell to reach almost 16 inches in length, but that's the largest ever reported (Kinch 2002). Thus, you shouldn't expect any given specimen you purchase to get so big. In fact, McMichael (1974) did a survey of several hundred maximas in the wild and reported that only 3% were larger than 9 inches and the largest specimen found in the whole survey was only 9.8 inches. So, that record holding 16-inch specimen was quite an anomaly.

When it comes to the soft parts, maximas typically extend their zooxanthellae-packed mantle tissue well beyond the upper edges of the shell. In fact, it's typically extended to the point that it completely obscures the shell from view when looking down on one. The mantle can also come in such a wide range of colors and patterns that there really is no standard color, although blue is the most common. As noted, the patterns covering it may also be striped, sprinkled, spotted, blotched, marbled, etc. and quite fancy, which is why various specimens are often called things like teardrop maximas, striped maximas, super maximas, or even ultra maximas, etc.

Still, the only patterns that are relatively consistent in how they look are that of the teardrop and striped varieties. Teardrop maximas may vary significantly in color, but they tend to have the same sort of pattern covering their mantle, being covered in teardrop-shaped splotches, while striped maximas tend to have a dark, solid background color with thin radiating stripes of blue, yellow, or white. Other than that, the mantle has rows of simple, closely-spaced, dark eyes near the outer edge and sometimes has numerous eye-tipped tubercles/protrusions on its upper surface, too. The large mouth-like opening in it (called the inhalent siphon) is also ringed with numerous simple, small tentacles that usually lack anything more than very fine branches.

Now, as I said above, maximas are indeed easily confused with croceas because both species have relatively large and often brightly-colored mantles with small tentacles around their inhalent siphons. The vast majority of maximas has elongated shells with lots of scutes, while almost all croceas have shorter, taller shells that lack scutes or only have a few small ones. But, there are exceptions, which lead to this confusion. A typical crocea's shell lacks scutes and is far less elongated than the shell of a typical maxima, but there are individuals of each species that are in between. Croceas can be rather elongated at times, and may actually have a lot of scutes, while some maximas may have rather short shells and lack scutes. So, I'll give you some additional pointers for trying to figure out which is which in case it isn't clear who is who.

First, a maxima's shell usually has larger, much more pronounced waves or folds than that of a crocea, as crocea's shells are typically relatively smooth. A maxima's shell sometimes has very sharply-pointed, almost triangular projections at the shell's upper edge, but crocea's are always more rounded and never sharp. Maximas can reach significantly larger sizes than croceas, as the record-holding crocea was only 6 inches long. So, anything larger than about 5 inches in length is almost certainly a maxima. There is no such thing as a teardrop crocea or a striped crocea. Croceas may have some stripes on them at times, but I've never seen one that had a solid background color with thin radiating stripes on top, or the characteristic droplets of a teardrop. And lastly, the tentacles around the inhalent siphon of a maxima are typically simple and un-branched, while those of a crocea are usually finely branched at their tips.

So, there is no straightforward single way to always ID both species correctly, but by looking at a combination of these features you can usually figure out just about any of them. I will admit though, over the years I've come across a handful of specimens that have been quite difficult to differentiate. At such times most folks just throw up their hands and declare that a hard-to-ID specimen in a hybrid between the two species, but after doing a lot of searching, reading, and asking clam farmers questions I'm still far from convinced that these two species can/do hybridize. That's a topic for another day, though.

Aquarium Care

When it comes to caring for maximas, water quality requirements are typical for reef aquariums in general. Basically, if you're successfully keeping corals alive and well, then your water quality is good enough for a maxima. On the other hand, if you're having problems maintaining excellent water quality - don't fool with any species of tridacnid.

When it comes to water motion, tridacnids live in reef and near-reef environments, and are regularly exposed to strong currents and wave activity. This is especially so for maximas, which often live right at the crest of a reef where waves break hardest. Thus, they are no strangers to strong, surging and turbulent water motion. However, in aquariums the flow tends to be quite linear and constant, as a pump outlet might blast water in one particular spot day and night at about the same volume per minute, and rarely creates any real surge or turbulence. So, you need to think about this when it comes to the placement of a maxima (or any other tridacnid) in an aquarium.

It's okay to expose maximas to a low velocity surge, or to turbulent flow, but putting them in a position where a pump constantly hits them with a strong, non-stop linear current is not recommended. Basically, any sort of current that causes the mantle to fold upwards too much, or over onto itself all the time is bad, as is any current that makes a specimen chronically retract its mantle. Thus, you can put one anywhere you like with respect to current, as long as it doesn't bring on either of these reactions. I'll also add that while they're almost always found on hard substrates and rubble in the wild, placing them on such is highly recommended, but is not required. Placing a specimen on sand/gravel won't kill them, but they often move around a lot, trying to find something to attach their byssus to. Next is lighting, which not surprisingly is of critical importance.

Maximas live at relatively shallow depths where they receive relatively intense light, so fluorescent lighting will only suffice in shallow tanks, or if a specimen is placed on the rockwork near the water's surface in a deeper tank. I would try fitting as many bulbs into the canopy/fixture as possible at that, and mount the bulbs close to the water, and then place any specimens within a foot of the surface, preferably less. Some specimens may be able to get by at times with less light, or further down in deeper tanks, but I implore you to not take chances. Metal halide or comparable L.E.D. lighting is your best option.

I know that some people have gotten by with less, but when it comes down to it insufficient lighting is certainly one of the most common causes of losses. The problem is that corals are very simple organisms that have no real "guts" to speak of, while tridacnids have all the organs you'd expect to find in a higher animal. They've got stomachs, kidneys, gonads, gills, and even a heart. Thus, they are far more complex than you might think, and they use a lot of calories to keep everything running. So, it's a mistake to think that just because your lighting is bright enough to keep corals healthy and growing that they're necessarily bright enough to keep a maxima alive long-term.

To make matters worse, it can take a tridacnid months to slowly starve to the point of no return. So, everything can look fine for weeks on end, then a specimen may seem to just up and die for no apparent reason when it was really starving the whole time. Every maxima is genetically different at that, and long-term experience has proven that some individuals can get by with less while others need much more, even though they may be the same species and even the same size and color. To add, you cannot give a tridacnid too much light as long as a specimen is given time to adapt to intense lighting, so it's better to err on the bright side than the dim side. For more on this, refer to my article On Lighting for Tridacnid Clams in the March 2011 issue, and for even more than that see my book Giant Clams in the Sea and the Aquarium.

Lastly, there's the question of whether or not you need to feed a maxima in an aquarium. As covered, all tridacnids are filter-feeders, yet their zooxanthellae can cover a great deal of their nutritional needs, and they're able to absorb pretty much everything else they need directly from seawater. In fact, if provided with enough light, maximas of any size have no need to filter feed and can thrive in particulate-free water as long as there are enough dissolved nutrients present. Controlled experiments by Fitt & Trench (1981) proved that tridacnids can do without, and I kept them for years before anyone was talking about adding phytoplankton to aquaria, much less sold any in a bottle. You can get all the details in my article Tridacnid Clams (Usually) Don't Need to Be Fed in Aquaria in the July 2010 issue, but I'll give you some basic info on the subject anyway.

When you feed your fishes some amount of the food won't get eaten and becomes detrital particles, which maximas can filter out. Any uneaten food also releases nutrients into the water as it decomposes. Likewise, the food that is eaten by the fishes ends up becoming solid wastes that can also become detritus. However, even more importantly, fishes excrete dissolved substances that can be absorbed by a clam, too. For example, fishes give off dissolved ammonia as a waste product, but tridacnids can absorb it and use it as a source of nitrogen. Thus, when you feed your fishes, you're feeding your tridacnid(s), too.

So, the real question is whether or not there are enough fishes in your aquarium to support one or more tridacnids. While it's unlikely to happen, I suppose it is possible to have too low a fish load (or too high a tridacnid load depending on how you look at it) in an aquarium, which would mean that the amount of fish waste being produced would not be enough to support the needs of the clam(s). So, my advice is to refrain from taking any chances and use a quality phytoplankton product if you have any doubts. I have to say though, I imagine that very, very few hobbyists have problems due to nutrient levels that are too low since for most of us the fight is to prevent them from getting to high.

Anyway, I need to wrap things up, and unfortunately I'll going to end on a bad note. As gorgeous as they may be, most all experienced aquarists agree that maxima is the least hardy of the tridacnids. I've seen and heard of more losses of this single species than all the rest by far, and I think it's usually due to insufficient lighting. They are especially dependent on excellent water quality and intense lighting. So, if you don't have both, don't buy one of these.

I'll also add that despite their attractiveness, availability, and relatively low price, really small specimens are even more likely to pass away. In fact, I experienced so many losses of small maximas back in my selling days that I outright refused to order/sell them after a while, and I've heard the same from many other vendors, too. They didn't tolerate shipping and acclimation to aquarium life very well at all, and it was common for more to die in the first couple of weeks than to live. Stick with larger specimens, as in at least few inches long, and you'll have much better odds of success.

References

1. Fitt, W.K. and R.K. Trench. 1981. Spawning, development, and acquisition of zooxanthellae by Tridacna squamosa (Mollusca, Bivalvia). Biological Bulletin 161:213-235.
2. Jaubert, J. 1977. Light, metabolism, and the distribution of Tridacna maxima in a South Pacific atoll: Takapoto (French Polynesia). Proceedings of the 3rd International Coral Reef Symposium 1:489-494.
3. Kinch, J. 2002. Giant clams: their status and trade in Milne Bay Province, Papau New Guinea. TRAFFIC Bulletin 19(2):1-9.
4. McMichael, D.F. 1974. Growth rate, population size and mantle coloration of the small giant clam Tridacna maxima (Roding), at One Tree Island, Capricorn Group, Queensland. Proceedings of the Second International Coral Reef Symposium 1:241-254.
5. Pasaribu, B.P. 1988. Status of giant clams in Indonesia. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
6. Rosewater, J. 1965. The family Tridacnidae in the Indo-Pacific. Indo-Pacific Mollusca 1:347-396.

The CV Dinar aquaculture facility, which is more easily called a farm, is located on the northeast coast of Bali, not too far east of Tulamben. It's also around 6 degrees south of the equator meaning the water's warm and there's plenty of sun year round, which gives rise to wonderful coral reefs. And, needless to say, the diving in spots around the island are absolutely incredible.

Diving in many areas can be deceptive though, because you typically get to see the best, healthiest areas, while other locations may be in bad shape. Most everyone has heard of the spectre of coral bleaching that has affected so many reefs around the world, and then there are the added insults of pollution, over-collecting, dynamite fishing, shipwrecks, etc. that have all taken their toll on both corals and giant clams, as well. These are some of the reasons that many businesses are aquaculturing a variety of organisms for the aquarium hobby now, and why other organizations are doing the same for the purpose of restocking natural areas. Farming clams has also helped to satisfy the demand for giant clams as food in Asian countries, too.

Anyway, after contacting the farm, I was picked up by Aspari Rachman, the facility manager, and taken for a full tour of the whole place. It isn't particularly big, but they certainly squeeze a lot of livestock into what they have. There are about 30 large concrete grow-out and holding tanks, and quite a few other concrete and acrylic tanks used for various other purposes, too. They have an on on-site lab, and various other buildings, one of which is used to raise their own phytoplankton used to feed infant clams, and zooxanthellae for them, too.

They have a huge water intake system at the shore, which allows them to pump water directly from the sea, after which it's run through a series of baffles that contain progressively smaller gravels and sands that act as filters. This water is then pumped through the tanks, making it easy to maintain high water quality. And, in the case of infant clams, the water is also run through micron filters to remove any sorts of parasites, too. Thus, there is a constant turnover of fresh, clean seawater in the systems, with no other sorts of filtration. There's also no need for additional lighting either, as there's plenty of sunlight for free. In fact, the sun does such a good job that they have shade cloth over all the tanks to cut down the amount of light the inhabitants get, and to help keep leaves and such out of the tanks, too.

The Corals

They were growing several types of stony coral at the farm, primarily being Acropora and Seriatopora, and also had plenty of the soft/leather corals Sarcophyton and Sinularia, as well as a few others. All of these were attached to small pieces of rock (which I'll talk about below), and had started out as frags/cuttings from other larger specimens. All of these corals can easily be cut or broken into pieces, and the pieces will live and grow into new specimens. So, they do the same thing that's regularly done by hobbyists and businesses here, but on a much larger scale, and with one big difference. Once the frags/cuttings are made and are attached to a base, they're put in the sea instead of being kept in a tank for weeks or months.

The farm has numerous metal cages on hand, and the corals are placed in these where they can be kept together and get some protection from wave activity and predators, too. The cages are carried maybe 100 yards out off the beach and placed on the bottom in about 20 feet of water. Then they sit for quite a while, sometimes several months. Of course, when you're not paying for salt, additives, and lighting the amount of time they sit is determined by how fast they grow to the size the farm likes rather than moving them to market as soon as they get big enough for someone to want to buy them - and the farm likes them pretty big.

Once the corals have grown large enough to satisfy the farmers, the cages are pulled and the specimens are placed in holding tanks on land. Then they're bagged up and shipped out.

The Clams

The farm also raises all six species of giant clam commonly seen for sale over here, being Tridacna crocea, T. maxima, T. derasa, T. squamosa, T. gigas, and Hippopus hippopus. And, they raise H. porcellanus too, which I was looking forward to finally seeing. These are very difficult to find for sale, and haven't been seen in the U.S. market for many years as best as I know. I bought one about four years ago, and the supplier said it was the first they'd ever seen after being in the clam-selling business for over seven years. Despite having at least a couple hundred mature specimens on hand, they told me that none were sent to the U.S. Anyway, while the corals are relatively easy to deal with, the clams take a lot more work, as they obviously can't be cut up to make more.

Giant clams are spawners, meaning when the time comes, individuals can spew out huge numbers of sperm and eggs into the water where some will meet the sperm and eggs of other clams. All of them are hermaphrodites when they are mature, so each can produce both sperm and eggs, too.

Well, on the farm they can be artificially enticed into spawning by injecting them with a small dose of the hormone serotonin. Once the hormone is injected into a clam's gonads, it will begin to spew clouds of sperm at first and then the eggs come after the sperm is depleted. So, in order to keep the clams from self-fertilizing (which makes for bad genetics), a clam is allowed to pump out the sperm and is then moved to another tank where the eggs can be released. Then the sperm can be collected from the water and intentionally mixed with the eggs from another clam. This sort of thing can be done with multiple clams, assuring that they have a good mixing of genetic material, which produces healthier clams.

After all of this, the eggs start to divide and grow, and soon become swimming larvae. At this stage they still do not have any symbiotic zooxanthellae though, as it's not passed from the parents to the offspring. Coral fragments already contain some, of course, but the clam larvae have to get their own complement of the algae by filtering some from the water.

So, the farmers grow zooxanthellae on site using a method they developed themselves, and add a little to the tanks that the larvae are in. The larvae then eat and hold onto it and allow it to reproduce inside their tissues. Other types of phytoplankton are also added, which the infant clams can also eat and used for food. Oddly enough, no one has figured out how it works, but the clams are able to keep the zooxanthellae alive for themselves, while simultaneously digesting other sorts of algae.

Anyway, the swimming larvae drop to the bottom after a short period of time and begin to undergo a metamorphosis, losing the ability to swim and taking on a new life upon the bottom. The farmers continue to add phytoplankton for two months, and they also begin adding nitrogen-based chemicals, too. Giant clams need a source of nitrogen and can extract it directly from seawater in the form of ammonia and nitrate, but giving them extra amounts can increase their growth rates significantly. So, things like ammonium nitrate (fertilizer) or sodium nitrate can be added to help speed things up.

Then, after sitting and growing in a holding tank, typically for more than a year, the clams are big enough to be placed in cages and put out to sea with the corals. At this time they still may be only an inch or two in length depending on the species, so many have a lot of growing to do before they can be sold as good-sized specimens. Some farms do sell clams while still at such a small size, but CV Dinar doesn't. I didn't ask why, but from what I understand, the small clams suffer significantly higher mortality rates, while bigger clams can handle shipping stresses much better.

Once in the cages, the clams are left in place for as long as three more years. So, you can see that this can be a slow process that takes a lot of patience. The timing of collection is primarily due to the species, I should also add, as some clams like T. gigas and T. derasa can potentially grow many times faster than other clams, like T. crocea.

Regardless, the farmers are constantly putting out hundreds of clams at a time, and everything ends up running like a conveyor belt. Small ones go in and big ones come out. The seafloor has plenty of space for cages too, so using them and keeping them in the sea means that there can be thousands of clams out at a time while the facility only needs enough room to hold the juvenile clams and those that are ready for export. Everything in between takes up no space in the tanks.

And Live Rock Too

By the way, the rock they need for the bases is made by hand on site by using local stone and cement, and they make lots of artificial live rock ranging from fist-size up to large mounds a couple of feet tall, too. Basically they just lay out some palm leaves on the ground and pile up the concrete-like mix to the desired size. The cement is allowed time to harden, and then the pieces are put in piles in the sea for several months. So, it becomes fully cured there, and also gets some stuff growing on it. In the end, much of it looks as good as much of the live rock coming from the Pacific and is sold as aquacultured live rock. But, they also hold onto some of it to use in re-stocking efforts.

Restocking Reefs

Again, many reefs are having problems, and the farm has been directed to help out by the Indonesian government. According to Aspari, they are allowed to operate the farm and export livestock as long as 10% of everything they grow is used to help the local reefs. So, they take some of the larger pieces of rock they produce and mount various corals and clams to them, then place them in areas that have been damaged in various ways. They were also trying to start new reefs in some spots, too. All in all, they're doing a great job and helping the hobby and the reefs.

The staff at the CV Dinar facility was exceptionally nice and very knowledgeable, but I have no experience with them on the exporting and business end. This article is by no means an advertisement for them, and is strictly for education.

Sources for more information on clam farming, which can be found online:

1. Ellis, S. 2000. Nursery and Growout Techniques for Giant Clams (Bivalvia: Tridacnidae). Center for Tropical and Subtropical Aquaculture Publication 143.
2. Ellis, S. 1998. Spawning and Early Larval Rearing of Giant Clams. Center for Tropical and Subtropical Aquaculture Publication 130.

As best as I can tell, for as long as tridacnids have been put in aquariums there has been much debate about how much light is needed to keep them healthy. I've heard all sorts of ideas here and there, and have even seen specific PAR values recommended for each species. However, most of what I've heard is bad advice, which is a result of the general lack of understanding of tridacnid biology. So, I'll try to straighten things out this month, and save the lives of some clams.

Tridacnids are complicated

To start, one of the biggest problems is the false notion that if various corals can be kept healthy under a given lighting system that tridacnids can be kept healthy under it, too. It's easy enough to see why many people would think this, but tridacnids are not corals.

Corals are very simple animals, and they don't really do too much when you think about it. They just sit there and soak up the sun, they don't move around, and they use very few calories from day to day to stay alive. Tridacnids, on the other hand, are actually very complicated animals with mouths, stomachs, intestines, kidneys, gonads, a beating heart, big gills, etc. They also use millions of tiny cilia to draw water into their bodies non-stop. Yes, they just sit around most of the time, but there's a heck of a lot more going on inside that shell than you might think. So, it takes a lot more calories to keep one alive.

Both can get some of their calories by eating plankton and such, but the vast majority of their needs are covered via the photosynthesis carried out by their complements of zooxanthellae. So, they both require light, and tridacnids generally need a lot more than corals. Therefore, you should never assume that good coral growth would equate to good clam growth under the same lighting. More on this in a minute, though.

Tridacnid species aren't all the same

Next, I'll point out that some tridacnid species can live at greater depths than others, and can survive with less light than others. Tridacna crocea, Hippopus hippopus, and H. porcellanus aren't found at depths greater than about 20 feet, and I don't think I've ever seen a single T. crocea living deeper than about ten. However, T. maxima and T. squamosa can be found at more than twice this depth, living down to around 50 feet, and T. gigas can be found even deeper, at around 65 feet. Then there's T. derasa, which can be found all the way down to around 80 feet, and the deepest-living species, T. tevoroa, which can be found down to a about 110 feet (but isn't offered in the hobby). This could be due to some structural differences between the various species, differences in their metabolism, or they may preferentially carry different strains of zooxanthellae, or all of the above, or something entirely different.

Regardless, intensity at the surface on a bright day in the tropics is around 2,500 µE/m²/s, but at 3 feet below the surface, depending on water clarity, light intensity is already reduced by about 15%, and by 110 feet it has dropped by about 94%. This means intensity drops to about 2,125 at just 3 feet and all the way down to about 150 by 110 feet, and that's in clear oceanic waters on a clear day. So, the deepest living tridacnid has never been found where intensity is lower than about 150 µE/m²/s, and all the rest live in waters where the intensity is higher.

By comparison, I've taken light readings in a couple of relatively dim reef aquariums lit with fluorescent bulbs and found that there are many stony corals that can live and grow under less light than this. Some examples are (in µE/m²/s):

Coral and Light Measurements

Coral Species	µE/m2/s
Pachyseris rugosa	110
Montipora capitata	110
Montipora spongodes	110
Pocillopora sp.	107
Montipora sp.	100
Monitpora digitata	95
Acropora cervicornis	80
Montastrea sp.	80
Acropora millepora	79
Scolymia sp.	70
Turbinaria peltata	64
Turbinaria reniformis	58
Fungia sp.	54
Euphyllia cristata	52
Trachyphyllia geoffroyi	40
Caulastrea furcata	32

Again, all of these were healthy and growing, so it should be clear that you could have a reef aquarium where the light intensity is less than 150 µE/m²/s and still have lots of growing corals, while not having enough light to keep any species of tridacnid healthy.

Anyway, I can tell you for sure that trying to get a T. crocea to live on the sparse light a T. derasa might receive at 80 feet just isn't going to work. Likewise, T. derasa can't live side by side with T. tevoroa at 110 feet. So, how much light is needed depends a lot on which species of tridacnid is being considered.

Individual tridacnids of each species aren't all the same, either

In addition to these species-level differences, there's also variability between individuals. There are countless subtle genetic differences that can make one clam more fit than another under the same conditions, even if they are the same species. Individuals may be carrying different strains of zooxanthellae, too. So, all of the members of a given species can't necessarily adapt to the same minimum light intensity, either. Sibling clams can grow at different rates and grow to different sizes, etc. under the same environmental conditions due to genetic differences, and I'm certain that some clams have varying abilities to deal with more or less light, too.

For example, I've seen areas where there are hundreds of T. maxima within a few feet of the surface in an area of sloping reef, but their numbers dropped off drastically within the next 20 feet depth, and almost none were living within the last 20 feet of their maximum reported depth. Actually, I'm pretty sure I've never come across one any deeper than about 35 feet. The same pattern of distribution is generally seen with the other species, too. Many individuals in shallower, brighter waters, with abundance dropping steeply as the depth approaches their reported maximum depth of occurrence.

Still, the salinity and temperature are essentially the same across these depths, and larval clams are at the mercy of waves and currents for several days, which can scatter them all over the place. This means that while the larvae are spread across a reef and nearby waters, the ones that settle in shallow waters are apparently more likely to survive while those that settle into deeper waters are not. So, it would seem that some individuals, for some reason(s), are better able to tolerate lower illumination than others, and go on to survive where others can't. They're the tough ones.

Further discussion and my recommendations

With this in mind, you should be able to see that there's no way to come up with a single number that would be the exact minimum amount of light that a species of clam can live under, because one clam's need for light is not necessarily the same as another clam's, even if they're the same species. Basically, the idea of asking for a specific lighting number would be like asking how many calories a day a Cocker Spaniel needs to survive without knowing its age, size, metabolic rate, etc.

This is very important to remember, as you will always want to provide at least enough light to keep any clam of a given species alive, not the minimum that you think an individual of the species could possibly live under. Of course, there are literally hundreds of bulbs and possible combinations of bulbs that can be used over reef aquariums, and they can get dimmer with age, as well. So, I obviously won't be covering every possibility below, but will give some conservative recommendations based on personal experiences and the advice of numerous other experienced aquarists.

To start, I'll say that all available species of tridacnids can and have been successfully kept under fluorescent lighting systems using high-output bulbs with good reflectors and/or metal halide bulbs. So, it is certainly possible to provide what they need through the use of commonly-offered lighting systems.

Still, in the case of T. crocea, which is apparently the most light-hungry species of the bunch, fluorescent lighting will only suffice in very shallow tanks, or if a specimen is placed very near the water's surface in a deeper tank. I would highly recommend squeezing as many bulbs into the canopy/fixture as possible at that, and then mount the bulbs so that they are as close to the water as possible, and then place the specimen within a foot of the surface, preferably less. Again, some individuals (the "tough" ones) may be able to get by at times with less light, or further down in deeper tanks, but I implore you to not take chances. So, I have to say that metal halide lighting is really the way to go for this species.

Moving along, H. hippopus and H. porcellanus are the other shallowest-living species, and I say give them as much light as you would give a T. crocea. Again, several high-output fluorescents will probably suffice over small tanks, but metal halide lighting is still preferred, and is required for deeper tanks.

T. maxima can live at over twice the depth that these other three can, and should be able to get by with much less light. So, many individuals can be kept under fluorescent systems, even if they're on the bottom of shallow to medium size tanks, as long as there are plenty of bulbs in use. But, they're far more abundant in shallow waters, and much less so at the deeper end of their range, so I still say you should play it safe and go with metal halides, or at least place specimens closer to the bulbs in medium to large size tanks.

T. squamosa can live at about the same depth as T. maxima, but from what I've seen, they don't drop of in numbers with depth to the degree that the other species do. Thus, they seem to be generally better at living under reduced light than T. maxima is, despite the fact that both of these species have the same reported maximum depth of occurrence. This observation has been backed up by my experiences with them in aquariums too, as they've categorically been more tolerant of lower light/greater depth in tanks. Thus, I think it's safe to say that T. squamosa can typically be kept under fluorescent lighting at the bottom of both small and medium size tanks without worry (again, as long as there are several bulbs with reflectors). But, I still say get metal halides for deeper tanks.

T. gigas, on the other hand, is very uncommon near its maximum reported depth, so I'd treat them the same as T. squamosa, even though they have been found many feet deeper. Fluorescents will do in small to medium size tanks, but metal halides should be used for deeper ones. Note that these are giants though, and it's probably best that you don't bother trying to keep a T. gigas in a relatively small tank anyway. So, I say keep a T. gigas in a big tank with metal halides, unless you're absolutely sure that you'll be getting a bigger tank in the (near) future, or can find your oversized clam a new home somewhere else.

Lastly, there's T. derasa, the deepest living species we can get. T. derasa tends to be especially hardy and while using several fluorescent bulbs and reflectors over small to medium tanks is all that is needed, this is the one species that I say can often be kept under fluorescent lights even if they are on the bottom of deeper aquariums. Not always though, as I had one in my 125 gallon tank for a few years that immediately stopped growing after I switched from three 175w metal halides and two 165 V.H.O. fluorescents to 14 three-foot T-5 bulbs with reflectors (seven bulbs over each half of the tank). Even after a few weeks it still didn't resume its growth, and I had to remove it. So, I still say use metal halides if at all possible, just to be sure.

Speaking of growth, watching for it is the key to figuring out if you really have enough lights. If your water quality is up to par, and a clam is free of disease, it should add on new shell material if it's getting enough light. So look for new, white material at the rim of the shell. If there's no growth, then the lights are probably too dim. This is important to remember because tridacnids can take months to slowly starve to death, and everything can look fine right up to that point. If they're slowly starving, they won't be doing any growing, though.

To summarize, it is impossible to give a single number recommendation when it comes to tridacnids' lighting requirements, even for a particular species. Each clam is genetically different, and some members of a given species will need more light than others. There is no way to determine this by looking at them though, so to be safe you need to provide enough light to keep any member of the species alive, and the best way to do this is to use intense metal halide lighting, or a fluorescent lighting system that includes quality reflectors and as many bulbs as will fit over the tank. If you're not sure if your lights are bright enough, always look for shell growth, and take action if there isn't any.

And don't forget, this and many other subjects are covered in great detail in Giant Clams in the Sea and the Aquarium, so grab a copy if you want to do some further reading on the topic.

Our examination of parasitic copepods will conclude this month with an examination of those 'bugs' known to infest soft corals, gorgonians and Tridacna clams. Oddly, no reports are known to me of hobbyists observing any of these parasites, and no information has been presented in hobby literature that I am aware of.

This brings up a couple of questions: Are these copepods restricted to geographical areas where collection of livestock for aquaria is not practiced? Or are we hobbyists, as a group, in need of honing our powers of observation? The goal of this article is to present copepods known to infest marine invertebrates (other than stony corals) popularly found in our captive reefs. Perhaps lack of documentation of these parasites within aquaria is simply due to their small size (usually, but not always, less than 1 millimeter in length). In addition, these copepods sometimes assume the color of their host, possibly indicating ingestion of host tissues.

A listing of parasites found on (or in) soft corals, anemones, zoanthids, gorgonians, and Tridacna clams is found at the conclusion of this article in Table 1.

I have made every attempt to update the taxonomic status of copepods listed in this article, and, in many cases, the status of the host as well. Often, the original Latin name of the animal is listed in parentheses. Sizes of the copepods are the maxima reported.

Parasites of Tridacna and Hippopus Clams

It should come as little surprise that Tridacna clams can be victims of parasitic copepods. It would seem that any animal not enduring parasitic infestations would be the exception.

Examples of Tridacna parasites include protozoa (Fatheree, 2006) and Pyramidellid snails (Tathrella iredalei; Heslinga et al., 1990). However, little popular literature offers information concerning copepod parasites of clams popularly kept in aquaria including species of genera Tridacna and Hippopus.

We'll begin our examination with copepods found in genus Anthessius.

Anthessius alatus

• Hosts: Tridacna gigas, T. maxima, T. noae (taxon no longer recognized), and T. squamosa
• Order: Poecilostomatoida
• Family: Anthessiidae
• Locality: Red Sea (T. noaea); Madagascar (T. squamosa); Eniwetok Atoll, Marshall Islands (T. squamosa, T. maxima, T. gigas), and New Caledonia (T. squamosa and T. maxima)
• Reference: Humes, 1973

Anthessius amicalis

• Hosts: Tridacna enlongata (= T. maxima), T. maxima, T. squamosa and Hippopus hippopus
• Order: Poecilostomatoida
• Family: Anthessiidae
• Locality: Eniwetok Atoll, Marshall Islands; New Caledonia; Red Sea
• Reference: Humes, 1973

Anthessius solidus

• Host: Tridacna squamosa
• Color: Opaque, with red eye
• Order: Poecilostomatoida
• Family: Anthessiidae
• Locality: Eniwetok Atoll, Marshall Islands
• Reference: Humes, 1973

Lichomolgus hippopi

• Host: Hippopus hippopus
• Order: Poecilostomatoida
• Family: Lichomolgidae
• Reference: Humes, 1976

Lichomolgus tridacnae

• Hosts: Tridacna gigas and Tridacna squamosa
• Color: Opaque, with red eye
• Order: Poecilostomatoida
• Family: Lichomolgidae
• Locality: Eniwetok Atoll, Marshall Islands
• Reference: Humes, 1972

Paclabius tumidus

• Hosts: Tridacna squamosa; Tridacna sp.
• Maximum Reported Size, female: 6mm (Kossmann, 1877)
• Maximum Reported Size, male: 2.11mm
• Color: Opaque, with red eye
• Order: Poecilostomatoida
• Family: Lichomolgidae
• Locality: Philippines (Kossmann); New Caledonia, (Humes)
• Reference: Humes, 1973; Humes and Stock, 1973, Kossmann, 1877

Tridachnophilus or Tridacnophilus

Nair (1988) moved Anthessius spp. associated with Tridacna clams to a new genus - Tridachnophilus. However, this synonym is no longer accepted, and Anthessius is correct.

Parasites of Gorgonians

I've taken the liberty of including hexacorals Antipathes in this grouping, though it is technically incorrect. Gorgonians include sea fans, sea whips, and others. In any case, gorgonians are potential victims of copepod parasites.

Acanthomolgus aequiseta

• Host: Muricea laxa
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Stock, 1975

Acanthomolgus affinis

• Host: Plexaura homomalla
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Stock, 1975

Acanthomolgus arctatipes

• Host: Echinogorgia sassapo
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes, 1974

Acanthomolgus astrictus

• Host: Acanthogorgia aspera
• Maximum Reported Size, female: 0.99mm
• Maximum Reported Size, male: 0.78mm
• Color: Mimics (attributable to?) the coloration of the host: Slightly reddish, egg sacs reddish-brown or gray, red eye
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Acanthomolgus bayeri

• Host: Pseudoplexaura porosa
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Bermuda
• Reference: Humes, 1971

Acanthomolgus bilobipes

• Hosts: Antillogorgia acerosa and Antillogorgia elastica
• Maximum Reported Size, female: 0.98mm
• Maximum Reported Size, male: 0.79mm
• Color: Translucent to very light tan, the eye is red.
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Curacao, West Indies
• Reference: Humes and Stock, 1973

Acanthomolgus combinatus

• Host: Echinogorgia sassapo
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes, 1974

Acanthomolgus dionyx

• Host: Pseudopterogorgia americana
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Stock, 1975

Acanthomolgus eminulus

• Host: Muricea california
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Ewbel, 1977

Acanthomolgus gentilis

• Host: Umbellulifera striata
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974
• Comment: Also a parasite of soft corals such as Dendronephthya

Acanthomolgus hales

• Host: Solenocaulon tortuosum
• Maximum Reported Size, female: 0.84mm
• Maximum Reported Size, male: 0.67mm
• Color: Opaque in transmitted light, eye is red
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974

Acanthomolgus hians

• Host: Siphonogorgia pichoni
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974

Acanthomolgus longispinifer

• Host: Siphonogorgia pichoni
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974

Acanthomolgus plantei

• Host: Umbellulifera striata
• Maximum Reported Size, female: 0.99mm
• Maximum Reported Size, male: 0.86mm
• Color: Opaque in transmitted light, eye is red
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974

Doridicola botulosus (formerly Metaxymolgus botulosus)

• Hosts: Eunicella stricta and Paramicea chameleon
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973

Paramolgus clavatus

• Host:Coelogorgia palmosa
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Paramolgus constrictus

• Host: Antipathes ericoides (wire coral)
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Paramolgus insectus

• Hosts: Antipathes abies, Antipathes myriophylla, and Antipathes sp. (spinescens?) - 'wire corals'
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Telestacicola angoti

• Hosts: Coelogorgia palmosa and Muricella rubra robusta
• Maximum Reported Size, female: 0.95mm
• Maximum Reported Size, male: 0.74mm
• Color: Translucent in transmitted light, with the alimentary canal being orange red within the prosome but bluish in the urosome, the eye is red and the egg sacs are pale lavender to brown.
• Locality: Madagascar
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Parasites of Soft Corals

Soft corals are perhaps the most popular coral invertebrates maintained within captive reefs. Many (if not all) of the popular soft corals are subject to infestations by parasitic copepods.

Acanthomolgus abonensis

• Host: Nephthea galbuloides
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Kim, 2007

Acanthomolgus boholensis

• Host: Dendronephthya puetteri
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes, 1973

Acanthomolgus cuneipes

• Hosts: Dendronephthya mucronata and Stereonephthya acaulis
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Acanthomolgus exilipes

• Hosts: Dendronephthya koellikeri, Dendronephthya mucronata, Dendronephthya regia, Dendronephthya speciosa, Dendronephthya stocki, and Stereonephthya cordylophora
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Acanthomolgus fissisetiger

• Hosts: Lemnalia humesi, Stereonephthya acaulis, and Stereonephthya papyracea
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Acanthomolgus gentilis

• Hosts: Dendronephthya koellikeri, Dendronephthya lokobeensis, Dendronephthya mucronata, Stereonephthya acaulis, and Stereonephthya cordylophora
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974

Acanthomolgus varirostratus

• Hosts: Dendronephthya cirsium, Dendronephthya koellikeri, Dendronephthya lokobeensis, Dendronephthya lokobeensis, Dendronephthya regia, Dendronephthya speciosa, Dendronephthya stocki, and Stereonephthya cordylophora
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974

Acanthomolgus verseveldti

• Hosts: Heteroxenia elisabethae, Heteroxenia fuscescens, and Xenia lepida
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1974
• Comment: Also known as Lichomolgus verseveldti

Ansiomolgus inciscus

• Host: Sarcophyton ehrenbergi
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973

Ansiomolgus insolens

• Host: Lobophytum crassum
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973

Ansiomolgus protentus

• Hosts: Lobophytum crebriplicatum, Sarcophyton glaucum, Sarcophyton globosum
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973; Humes, 1975

Ascetomolgus plicatus

• Host: Studeriotes semperi
• Maximum Reported Size, female: 0.90mm
• Maximum Reported Size, male: 0.74mm
• Color: Opaque, red is eye, egg sacs are gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Colobomolgus cristatus

• Host: Sinularia leptoclados
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Colobomolgus dentipes

• Host: Sinularia humesi
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Colobomolgus laboutei

• Host: Sinularia leptoclados
• Maximum Reported Size, female: 0.96mm
• Maximum Reported Size, male: 0.63mm
• Color: Opaque in transmitted light, eye is red.
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Contomolgus lokobeensis

• Hosts: Studeriotes semperi and Dendronephthya stocki
• Maximum Reported Size, female: 1.49mm
• Maximum Reported Size, male: 1.22mm
• Color: Opaque in transmitted light, eye is red, egg sacs are gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Doridicola aculeatus (formerly Metaxymolgus aculeatus)

• Hosts: Lemnalia madagascarensis, Lemnalia sp., Litophyton arboretum, Nephthea aberrans , Nephthea amentacea, Nephthea bumasta, Nephthea crassa, Nephthea filamentosa, Nephthea galbuloides, Nephthea lanternaria, Nephthea sphaerophora, Nephthea tixierae, Stereonephthya nosybearia and Stereonephthya scaphis
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973

Doridicola antheliae (formerly Metaxymolgus antheliae)

• Hosts: Anthelia glauca and Anthelia ternatana
• Maximum Reported Size, female: 1.14mm
• Maximum Reported Size, male: 0.85mm
• Color: Opaque in transmitted light, eye is red, egg sacs gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973

Doridicola bulbipes

• Hosts: Alcyonium acaule and Parerythropodium coralloides
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: France, Spain
• Reference: Humes and Stock, 1973

Doridicola cincinnatus (formerly Metaxymolgus cincinnatus)

• Host: Cladiella pachyclados
• Maximum Reported Size, female: 1.63mm
• Maximum Reported Size, male: 1.43mm
• Color: Opaque, eye red, egg sacs gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes, 1975

Doridicola cinctus

• Host: Psammogorgia ramosa
• Reference: Humes, 1975

Doridicola comparatus (formerly Metaxymolgus comparatus)

• Host: Xenia membranacea
• Maximum Reported Size, female: 2.24mm
• Maximum Reported Size, male: 1.82mm
• Color: Opaque, eye red, egg sacs gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes, 1975

Doridicola foxi

• Hosts: Cladiella krempfi, Cladiella lacinosa, Cladiella latissima, Cladiella pachyclados, and Cladiella sphaerophora
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Doridicola hetaericus

• Hosts: Cladiella krempfi, Cladiella laciniosa, andCladiella polyclados
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes, 1975

Doridicola mimicus (formerly Metaxymolgus mimicus)

• Host: Cladiella pachyclados
• Maximum Reported Size, female: 1.73mm
• Maximum Reported Size, male: 1.22mm
• Color: Opaque, eye red, egg sacs gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes, 1975

Doridicola patulus

• Host: Sinularia mayi
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes, 1975

Doridicola praelongipes (formerly Metaxymolgus praelongipes)

• Host: Xenia membranacea
• Maximum Reported Size, female: 2.30mm
• Maximum Reported Size, male: Unknown
• Color: Opaque, eye red, egg sacs gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes, 1975

Doridicola singularipes

• Hosts:Parerythropodium rubiginosum and
• Parerythropodium sp.
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Frost, 1964

Doridicola spinulifer (formerly Metaxymolgus spinulifer)

• Hosts: Lemnalia africana, Lemnalia amabilis, Lemnalia cervicornis, Lemnalia crassicaulis, Lemnalia digitata, Lemnalia elegens, Lemnalia flava, Lemnalia longiramus, Lemnalia madagascarensis, Lemnalia tenuis, Paralemnalia clavata, Paralemnalia polydactyla, andParalemnalia thyrsoides
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Frost, 1964

Meringomolgus fascetus

• Hosts: Sinularia minima and Sinularia polydactyla
• Maximum Reported Size, female: 1.44mm
• Maximum Reported Size, male: 1.20mm
• Color: Opaque in transmitted light, eye is red and egg sacs are gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Meringomolgus devotus

• Host: Sinularia leptoclados
• Maximum Reported Size, female: 1.46mm
• Maximum Reported Size, male: 0.92mm
• Color: Opaque in transmitted light, eye is red and egg sacs are gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Meringomolgus hamatus

• Hosts: Sinularia leptoclados, Sinularia humesi, and Sinularia maximus
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Monomolgus unihastatus

• Host: Anthelia sp.
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Color: Red eye
• Locality: Madagascar
• Reference: Humes and Stock, 1973
• Comment: Also found on Porites stony corals

Notoxynus mundus

• Host: Xenia membranacea
• Maximum Reported Size, female: 2.18mm
• Maximum Reported Size, male: 1.70mm
• Color: Slightly brownish, eye red, egg sacs gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: New Caledonia
• Reference: Humes, 1975

Paradoridicola adelphus

• Host: Sinularia pendunculata, Sinularia polydactyla, and Sinularia whiteleggei
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Paradoridicola glabripes

• Host: Xenia macrospiculata
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Paradoridicola squamiger

• Host: Sinularia polydactyla and Sinularia whiteleggi
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Paradoridicola sinulariae

• Host: Sinularia arborea
• Maximum Reported Size, female: 1.46mm
• Maximum Reported Size, male: 1.05mm
• Color: Opaque in transmitted light with a few red globules, the eye is red and egg sacs are opaque gray
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Paradoridicola triquetrus

• Host: Anthelia gracilis
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Paramolgus anomalus

• Host: 'Alcyonacean tissue'
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Southern coast of Arabia
• Reference: Humes and Stock, 1973

Paramolgus clavatus

• Hosts: Lemnalia longiramus, Lemnalia cervicornis, andLemnalia crassicaulis
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Paramolgus spathophorus

• Hosts: Sarcophyton glaucum, Sarcophyton trocheliophorum, and Sarcophyton acutangulum
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Paredromolgus decorus

• Hosts: Cladiella laciniosa, Cladiella latissima, and Cladiella sphaerophora
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Parategastes conexus

• Host: Stereonephthya ulicoides
• Maximum Reported Size (female): 0.41mm
• Maximum Reported Size (male): 0.43mm
• Color: Opaque pale grayish tan, eye red, genital area bright red, egg sacs gray.
• Order: Harpacticoida
• Family: Tegastidae
• Locality: Moluccas Islands
• Reference: Humes, 1984

Zamolgus acanthodes

• Host: Sinularia arborea
• Maximum Reported Size, female: 1.09mm
• Maximum Reported Size, male: 0.78mm
• Color: Translucent, with a few red globules within the prosome, the eye is red and the egg sacs are opaque
• Locality: Madagascar
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Zamolgus cracens

• Host: Cespitularia multipinnata
• Locality: Madagascar
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Dojiri, 1979

Zamolgus tridens

• Host: Cespitularia turgida
• Locality: Madagascar
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Reference: Humes and Stock, 1973

Parasites of Anemones

Anemones are quite popular inhabitants of reef aquaria, if sometimes only to act as a home to anemone fishes. We often think of successful maintenance of anemones as meeting their photosynthetic and nutritional requirements. Is there more we should consider? Can an active copepod infestation harm anemones, either through predation or their acting as vectors of disease?

Aspidomolgus stoichactinus

• Host: Stichodactyla gigantea (formerly Stoichactis helianthus)
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Barbados, Puerto Rico, Jamaica and the Bahamas
• Reference: Humes and Stock, 1973

Critomolgus actiniae (formerly Doridicola actiniae)

• Hosts: Actinia concentrica, Anemonia sculata, andActinia equina
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: England, France, Italy
• Reference: Humes and Stock, 1973

Doridicola antheae

• Host: Anemonia sculata
• Note: There is some doubt about the taxonomic status of this copepod - further descriptions are needed.

Doridicola cuspis (formerly Metaxymolgus cuspis)

• Hosts: Radianthis ritteri and Stoichactis giganteum (now Stichodactyla giganteum)
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Location: Madagascar
• Reference: Humes and Stock, 1973

Doridicola gemmatus

• Host: Stoichactis giganteum (now Stichodactyla giganteum)
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Doridicola magnificus

• Host: Stichodactyla giganteum (formerly Stoichactis giganteum)
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Doridicola mayorae

• Host: Stoichactis haddoni
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Paranthessius anemoniae

• Hosts: Anemonia sp., Anemonia sculata
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: France, Italy
• Reference: Humes and Stock, 1973

Parasites of Zoanthids

Zoanthids have achieved a cult following among many reef aquarists, and with good reason. Their sometimes intense coloration combined with relative ease of maintenance has made them perennial favorites. However, successful husbandry should consider all relevant factors, including parasites.

Doridicola inaequalis

• Hosts: Palythoa liscia and Palythoa tuberculosa
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Ho, 1966 in Humes and Stock, 1973

Indomolgus brevisetosus

• Hosts: Palythoa tuberculosa and Palythoa liscia
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Indomolgus diversus

• Hosts: Palythoa tuberculosa and Palythoa liscia
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Ho, 1966

Temnomolgus erynotus

• Host: Palythoa tuberculosa
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Ho, 1966 in Humes and Stock, 1973

Parasites of False Corals (Corallimorpharians)

The grouping of 'false corals' includes genera Discosoma, Rhodactis, and many others. Although limited information is available, we as hobbyists should believe that all false corals species are potential victims of copepod parasites.

Paramolgus politus

• Host: Rhodactis rhodostoma
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Paramolgus simulans

• Host: Rhodactis rhodostoma
• Order: Poecilostomatoida
• Family: Rhynchomolgidae
• Locality: Madagascar
• Reference: Humes and Stock, 1973

Conclusions

It should be apparent that many (if not most or even all) marine invertebrates popular in reef aquaria are subject to infestations by parasitic copepods. However, we can only speculate at the amount of harm they actually cause.

As a very rough analogy, we can examine how a common parasite might affect its host. Our example is an insect - a flea. They are an inconvenience to many animals but usually not fatal. However, under different circumstances the flea is a vector of deadly disease. Consider the role of fleas in the transmission of bubonic plague (the Black Death) to humans. Fleas were carriers of bacteria obtained while feeding on the blood of rats, and transmitted this ailment to humans.

Are aquatic copepods capable of transmitting disease among marine invertebrates? Ivanenko and Smurov (1996) raise the interesting possibility that copepods might introduce pathogens to its host. This could perhaps explain why some copepods infestations are relatively harmless, while seemingly mild cases of parasitism cause rapid decline and death of the host. As a footnote, the pathogenic bacteria Vibrio has been found attached to some copepods' exoskeletons (though not specifically 'coral' copepods or any Vibrio species known to infect scleractinians).

Disease issues aside, the potential of harm to the coral host by parasites is likely best considered on a case by case basis. It is difficult to believe a large soft coral existing under conditions of optimal lighting, water motion and nutrition could be significantly harmed by even a severe parasite infestation. On the other hand, non-photosynthetic corals are often nutritionally deprived due to either lack of proper food or poor water motion (or their synergistic effects). In this case it seems quite possible that the coral animal could have difficulty in coping with the amount of energy required for tissue repair and maintenance.

The amount of trauma inflicted by parasitic copepods should be considered. A small amount of damage to the thin layers of tissues covering a small-polyp stony coral (such as Acropora species) could possibly have more of an impact on its health than, say, the amount of damage done to a fleshy soft coral.

With as much information as we have, our understanding of soft coral parasites leaves much to be desired. At present, even the acknowledgement of their existence by hobbyists is extremely rare, much less confirmations of these copepods' presence in aquaria. Do these parasites exist on the external portions of corals, or are they endoparasites inhabiting the polyp guts?

We have little reason to believe that existing treatments and quarantine/pretreatment protocols would not be effective against these 'bugs'. However, this too remains to be proven.

This article concludes our brief and incomplete look at copepods capable of potentially harming our captive animals. However, the series will continue with reports of other parasites, including nudibranchs, sea spiders and other 'creepy-crawlies'.

Acknowledgements

Many thanks to Steve Ruddy of Coral Reef Ecosystems (www.coralreefecosystems.com) and Michael P. Janes of AquaTouch (www.aquatouch.com) for providing photographs for this article.

Comments? Questions? Please leave correspondence below.

Table One. Listing of Parasites by Host

Invertebrate Host	Parasite
Acanthogorgia aspera	Acanthomolgus astrictus
Acanthogorgia aspera	Thamnomolgus robustus
Actinia concentrica	Critomolgus actiniae
Actinia equina	Critomolgus actiniae
Alcyonacean tissue'	Paramolgus anomalus
Alcyonium acaule	Doridicola bulbipes
Anemonia sculata	Critomolgus actiniae
Anemonia sculata	Doridicola antheae
Anemonia sculata	Paranthessius anemoniae
Anthelia glauca	Doridicola antheliae
Anthelia gracilis	Paradoridicola triquetrus
Anthelia sp.	Monomolgus unihastatus
Anthelia ternatana	Doridicola antheliae
Antillogorgia ascerosa	Acanthomolgus cuneipes
Antillogorgia elastica	Acanthomolgus bilobipes
Antipathes	Thamnomolgus robustus
Antipathes abies	Paramolgus insectus
Antipathes exicoides	Paramolgus constrictus
Antipathes myriophylla	Paramolgus insectus
Antipathes myriophyllia	Thamnomolgus nodulus
Antipathes spinescens	Paramolgus insectus
Cespitularia multipinnata	Zamolgus cracens
Cespitularia turgidia	Zamolgus tridens
Cladiella krempfi	Critomolgus foxi
Cladiella krempfi	Doridicola hetaericus
Cladiella laciniosa	Doridicola hetaericus
Cladiella laciniosa	Paredomolgus decorus
Cladiella lacinosa	Critomolgus foxi
Cladiella latissima	Critomolgus foxi
Cladiella latissima	Paredomolgus decorus
Cladiella pachyclados	Critomolgus foxi
Cladiella pachyclados	Doridicola cincinnatus
Cladiella pachyclados	Doridicola hetaericus
Cladiella pachyclados	Doridicola mimicus
Cladiella sphaerophora	Critomolgus foxi
Cladiella sphaerophora	Paredomolgus decorus
Coelogorgia palmosa	Paramolgus clavatus
Coelogorgia palmosa	Telestacicola angoti
Dendronephthya cirsium	Acanthomolgus varirostratus
Dendronephthya koellikeri	Acanthomolgus exilipes
Dendronephthya koellikeri	Acanthomolgus gentilis
Dendronephthya koellikeri	Acanthomolgus varirostratus
Dendronephthya lokobeensis	Acanthomolgus gentilis
Dendronephthya lokobeensis	Acanthomolgus varirostratus
Dendronephthya mucronata	Acanthomolgus cuneipes
Dendronephthya mucronata	Acanthomolgus exilipes
Dendronephthya mucronata	Acanthomolgus gentilis
Dendronephthya mucronata	Acanthomolgus varirostratus
Dendronephthya puetteri	Acanthomolgus boholensis
Dendronephthya regia	Acanthomolgus exilipes
Dendronephthya regia	Acanthomolgus varirostratus
Dendronephthya sp.	Acanthomolgus varirostratus
Dendronephthya speciosa	Acanthomolgus exilipes
Dendronephthya speciosa	Acanthomolgus exilipes
Dendronephthya speciosa	Acanthomolgus varirostratus
Dendronephthya stocki	Acanthomolgus exilipes
Dendronephthya stocki	Acanthomolgus varirostratus
Dendronephthya stocki	Contomolgus lokobeensis
Echinogorgia sassapo	Acanthomolgus affinis
Echinogorgia sassapo	Acanthomolgus combinatus
Eunicella stricta	Doridicola botulosus
Heteroxenia elisabethae	Acanthomolgus verseveldti
Heteroxenia fuscescens	Acanthomolgus verseveldti
Hippopus hippopus	Anthessius amicalis
Lemnalia africana	Doridicola spinulifer
Lemnalia africana	Doridicola spinulifer
Lemnalia amabilis	Doridicola spinulifer
Lemnalia amabilis	Doridicola spinulifer
Lemnalia cervicornis	Doridicola spinulifer
Lemnalia cervicornis	Doridicola spinulifer
Lemnalia cervicornis	Paramolgus clavatus
Lemnalia crassicaulis	Doridicola spinulifer
Lemnalia crassicaulus	Doridicola spinulifer
Lemnalia crassicaulus	Doridicola spinulifer
Lemnalia crassicaulus	Paramolgus clavatus
Lemnalia digitata	Doridicola spinulifer
Lemnalia digitata	Doridicola spinulifer
Lemnalia digitata	Doridicola spinulifer
Lemnalia elegans	Doridicola spinulifer
Lemnalia elegans	Doridicola spinulifer
Lemnalia flava	Doridicola spinulifer
Lemnalia flava	Doridicola spinulifer
Lemnalia humesi	Acanthomolgus fissisetiger
Lemnalia longiramus	Doridicola spinulifer
Lemnalia longiramus	Doridicola spinulifer
Lemnalia longiramus	Doridicola spinulifer
Lemnalia longiramus	Paramolgus clavatus
Lemnalia madagascarensis	Doridicola spinulifer
Lemnalia madagascarensis	Doridicola spinulifer
Lemnalia madagascarensis	Doridicola spinulifer
Lemnalia sp.	Doridicola spinulifer
Lemnalia tenuis	Doridicola spinulifer
Litophyton arboreum	Doridicola aculeatus
Lobophytum crassum	Ansiomolgus insolens
Muricea california	Acanthomolgus eminulus
Muricea laxa	Acanthomolgus aequiseta
Muricella rubra robusta	Telestacicola angoti
Nephthea aberrans	Doridicola aculeatus
Nephthea amentacea	Doridicola aculeatus
Nephthea bumasta	Doridicola aculeatus
Nephthea crassa	Doridicola aculeatus
Nephthea filamentosa	Doridicola aculeatus
Nephthea filamentosa	Doridicola aculeatus
Nephthea galbuloides	Acanthomolgus abonensis
Nephthea lanternaria	Doridicola aculeatus
Nephthea sphaerophora	Doridicola aculeatus
Nephthea tixierae	Doridicola aculeatus
Palythoa liscia	Doridicola inaequalis
Palythoa liscia	Indomolgus brevisetosus
Palythoa liscia	Indomolgus diversus
Palythoa tuberculosa	Doridicola inaequalis
Palythoa tuberculosa	Indomolgus brevisetosus
Palythoa tuberculosa	Indomolgus diversus
Palythoa tuberculosa	Temnomolgus erynotus
Paralemnalia clavata	Doridicola spinulifer
Paralemnalia polydactyla	Doridicola spinulifer
Paralemnalia thyrsoides	Doridicola spinulifer
Paramuricea chameleon	Doridicola botulosus
Parerythrodium fulvum	Monomolgus unihastatus
Parerythropodium coralloides	Doridicola bulbipes
Parerythropodium fulvum	Monomolgus unihastatus
Parerythropodium rubiginosum	Doridicola singularipes
Parerythropodium sp.	Doridicola singularipes
Plexaura homomalla	Acanthomolgus arctatipes
Psammogorgia ramosa	Doridicola cinctus
Pseudoplexaura porosa	Acanthomolgus bayeri
Pseudopterogorgia americana	Acanthomolgus dionyx
Radianthus ritteri	Doridicola cuspis
Rhodactis rhodostoma	Paramolgus politus
Rhodactis rhodostoma	Paramolgus simulans
Sarcophyton acutangulum	Paramolgus spathophorus
Sarcophyton creriplicatum	Anisomolgus protentus
Sarcophyton ehrenbergi	Ansiomolgus incisus
Sarcophyton glaucum	Ansiomolgus protentus
Sarcophyton glaucum	Paramolgus spathophorus
Sarcophyton globosum	Ansiomolgus protentus
Sarcophyton trocheliophorum	Paramolgus spathophorus
Sinularia arborea	Paradoridicola sinulariae
Sinularia arborea	Zamolgus acanthodes
Sinularia humesi	Cologomolgus dentipes
Sinularia humesi	Meringomolgus hamatus
Sinularia leptoclados	Cologomolgus cristatus
Sinularia leptoclados	Cologomolgus laboutei
Sinularia leptoclados	Meringomolgus facetus
Sinularia leptoclados	Meringomolgus hamatus
Sinularia maxima	Meringomolgus hamatus
Sinularia mayi	Doridicola patulus
Sinularia minima	Meringomolgus devotus
Sinularia pedunculata	Paradoridicola adelphus
Sinularia polydactyla	Meringomolgus facetus
Sinularia polydactyla	Paradoridicola adelphus
Sinularia polydactyla	Paradoridicola squamiger
Sinularia whiteleggi	Paradoridicola adelphus
Sinularia whiteleggi	Paradoridicola squamiger
Siphonogorgia pichoni	Acanthomolgus hians
Siphonogorgia pichoni	Acanthomolgus longispinifer
Solenocaulon tortuosm	Acanthomolgus hales
Stereonephthya acaulis	Acanthomolgus cuneipes
Stereonephthya acaulis	Acanthomolgus fissisetiger
Stereonephthya acaulis	Acanthomolgus gentilis
Stereonephthya cordylophora	Acanthomolgus exilipes
Stereonephthya cordylophora	Acanthomolgus gentilis
Stereonephthya cordylophora	Acanthomolgus varirostratus
Stereonephthya nosybearia	Doridicola aculeatus
Stereonephthya papyracea	Acanthomolgus fissisetiger
Stereonephthya scaphis	Doridicola aculeatus
Stereonephthya sp.	Parategastes conexus
Stichodactyla gigantea	Aspidomolgus stoichactinus
Stichodactyla giganteum	Critomolgus gemmatus
Stichodactyla giganteum	Critomolgus magnificus
Stichodactyla giganteum	Doridicola cuspis
Stoichactis haddoni	Doridicola myorae
Studeroides semperi	Ascetomolgus plicatus
Studeroides semperi	Contomolgus lokobeensis
Tridacna gigas	Anthessius alatus
Tridacna gigas	Lichomolgus tridacnae
Tridacna maxima	Anthessius alatus
Tridacna maxima	Anthessius amicalis
Tridacna sp.	Paclabius tumidus
Tridacna squamosa	Anthessius alatus
Tridacna squamosa	Anthessius amicalis
Tridacna squamosa	Anthessius solidus
Tridacna squamosa	Lichomolgus tridacnae
Tridacna squamosa	Paclabius tumidus
Umbellulifera striata	Acanthomolgus gentilis
Umbellulifera striata	Acanthomolgus plantei
Xenia lepida	Acanthomolgus verseveldti
Xenia macrospiculata	Paradoridicola glabripes
Xenia membranacea	Doridicola comparatus
Xenia membranacea	Doridicola praelongipes
Xenia membranacea	Notoxynus mundus
Xenia viridis	Paradoridicola glabripes

References

1. Fatheree, J., 2006. Giant Clams in the Sea and the Aquarium. The Biology, Identification, and Aquarium Husbandry of Tridacnid Clams. Liquid Medium, Tampa. 227 pp.
2. Kossmann, R., 1877. Entomostraca (l. Thiel: Lichomolgidae). In: Zool. Ergeb. Reise Küstengelb. Rothen Meeres, erste Hälfte, IV: 1-24.
3. Heslinga, G., T. Watson and T. Isamu, 1990. Giant Clam Farming. Pacific Fisheries Development Foundation (NMFS/NOAA), Honolulu, Hawaii. 179 pp.
4. Humes, A., 1975. Cyclopoid copepods (Lichomolgidae) associated with alcyonaceans in New Caledonia. Smithsonian Contributions to Zoology, No. 191. Smithsonian Institution Press, Washington, DC.
5. Humes, A., and J. Stock, 1973. A revision of the Family Lichmolgidae Kossmann, 1877, cycloid copepods mainly associated with marine invertebrates. Smithsonian Contributions to Zoology, No. 127. Smithsonian Institution Press, Washington, DC.
6. Humes, A., 1973. Cyclopoid copepods associated with marine bivalve mollusks in New Caledonia. Cah. O.R.S.T.O.M., sér. Océanogr., Vol. XI, 1:3-25.
7. Humes, A., 1990. Synopsis of Lichomolgid copepods (Poecilostomatoid) associated with soft corals (Alcyonacea) in the tropical Indo-Pacific. Zool. Verh., 266:1-201.
8. Humes, A., 1973. Cyclopoid copepods of the genus Acanthomolgus (Lichomolgidae) associated with gorgonians in Bermuda. J. Nat. Hist. London, 7(1):85-115.
9. Humes, A. and G. Ewbel, 1977. Cyclopoid copepods of the genus Acanthomolgus (Lichomolgidae) associated with a gorgonian in California. Trans. Amer. Microsc. Soc., 96(1): 1-12.
10. Kim, I., 2005. Four new species of copepods (Crustacea) associated with gorgonacean corals (Cnidaria) from Bohol, Phillipines. Korean J. Syst. Zool., 21(2):121-191.
11. Kim, I., 2007. Copepods (Crustacea) associated with marine invertebrates from the Moluccas. Korean J. Systemat. Zool., Special Issue 6:1-126.
12. Stock, J., 1975. On twelve species of the genus Acanthomolgus (Copepoda: Cyclopoida: Lichomolgidae) associated with West Indian octocorals. Bijdragen tat de Dierkunde. 45(2): 237-269

Tridacnids, generally called giant clams, are common additions to reef aquariums, most of which belong to the genus Tridacna . However, there are two tridacnids available from time to time, which are not in the same genus with the rest of the bunch. These are Hippopus hippopus and Hippopus porcelanus , the former of which is far more likely to be seen for sale than the latter. Regardless, folks are generally unfamiliar with both of these species, so I'll fill you in.

Hippopus hippopus

Commonly called the hippopus clam, strawberry clam, horse's hoof clam, or bear paw clam, this species is typically found on reef flats, often in grassy areas, living on sandy to slightly muddy bottoms, or on coral fragments and gravels (Barnes 1984 and Govan et al . 1988). Shelley (1988) reported that juveniles are usually lightly byssally attached to the substrate, and that they typically stay attached until they are larger than 14cm. However, Pasaribu (1988) reported that hippopus clams are generally not attached to the substrate. This depends on size and substrate though, with juveniles being attached if possible, and larger clams living unattached and relying more upon their own weight to keep them in place. They also live from the intertidal zone down to about 6m.

Theirnatural range extends from the eastern Indian Ocean from Myanmar eastward across the Pacific Ocean to the Marshall Islands and to Fiji and Tonga, and from as far north as Japan down to the Great Barrier Reef, New Caledonia, and western Australia. However, hippopus has been heavily over-fished and is rare to extinct in many parts of this range (Wells 1997 and Raymakers et al . 2003).

Unlike the Tridacna species, hippopus' mantle, without exception, extends only to the upper margin of the shell. It does not extend laterally out of the shell, as is seen with the Tridacna species. The inhalent siphon, where water is drawn into the body chamber, has no tentacles around its margin, either. However, I have seen small protrusions around the margins of some specimens, and sometimes the siphon's margin can also be somewhat jagged in appearance or rather convoluted/frilly. The exhalent siphon, where water exits, is typically flattened and disc-like, forming a low cone with a circular opening.

This species can come in a few colors, but the vast majority has a predominantly yellowish-brown or olive-green mantle with white to cream or golden splotches and/or thin stripes. Others may be more gray in color, but that's about it. They often have considerable areas of rather translucent tissue with lighter or no color, as well.

Theshell is usually grayish-white, sometimes with a faint tinge of yellow or orange. However, unlike other tridacnids, it's oftentimes covered by irregularly-shaped red blotches. The shell commonly becomes highly encrusted by other organisms though, so these markings typically aren't visible on larger ones in the wild. It can also be very elongated with respect to the hinge, which is typically a bit more than 1/2 the length of the shell, and may be closer to 2/3 of its length for larger specimens. This allows the shell to gape open very widely. The shells are also strongly inflated, and hippopus is usually quite fat even at small sizes.

The shells can also have a variable number of folds/ribs, often having as many as 13 or 14, in a great range of sizes. However, typically only 5 to 8 of these are more pronounced than the others, and can be relatively convex and rounded, or more straight-angled and box-like. In addition, the larger folds also usually have small riblets on their surfaces, so that one large fold may appear be made of several smaller ones. They also lack the scale-like scutes commonly seen on Tridacna species like T. maxima and T. squamosa , but they're sometimes covered by small semi-tubular structures. These are especially common on smaller clams, and when present they can give the shell something of a prickly appearance.

The shell halves are symmetrical to each other and can close tightly. They're topped by rather unusual inter-digitating projections though, which are often quite squarish when the clams are young, and become more rounded as the clams grow. There are usually 8 to 12 of these. The byssal opening in the bottom of the shell is usually absent or quite small for juveniles, often being nothing more than a short slot that is closed completely later. This is expected, as hippopus typically maintains only a weak byssal attachment when young, if any at all, and always lives unattached when larger. The area around the byssal opening is rather unique, too, as it's ringed with numerous small, inter-digitating projections/teeth that are absent in Tridacna species.

They can also get quite large, as Rosewater (1965) reported that hippopus could grow to 40cm in length, with more recent references indicating even larger sizes. For example, Fossa & Nilsen (2002) say the maximum size is 50cm, while Knop (1996) says the record holder is housed at the Marine Science Institute of the University of the Philippines and measures in at 54cm. However, Fossa & Nilsen also reported that 40cm is usually the maximum size, and Smith (1898) wrote about an "unusually large specimen" from the Philippines that was only 34cm in length. So, don't expect one to reach such huge sizes in an aquarium.

Hippopus porcellanus

Commonly called the porcelain clam or China clam, this species is hard to come by in the U.S. A few years ago I bought one from Clams Direct, and the owner told me it was the first one he'd ever seen despite importing clams for over 7 years. I have never seen one offered at a shop, either. However, while visiting the C.V. Dinar coral and clam farm in Indonesia I saw that they had reared quite a few of them, all of which were going to the Japanese aquarium market. For that matter, most all of the best clams they had were going to Japan, too. After living there for two years, I can tell you that they get the best stuff across the board. They pay for it, too…

Anyway, like hippopus, porcellanus is typically found on reef flats, often in grassy areas, living on sandy bottoms (Pasaribu 1988 and Delbeek & Sprung 1994). Pasaribu (1988) also reported that porcellanus clams are "generally" not attached to the substrate, and that they also live from the intertidal zone down to only 6m. However, porcellanus has a far smaller natural distribution than hippopus, originally being found only in eastern Indonesia, the southern Philippines, Palau, and Papau New Guinea (Kinch 2002), and later in Malaysia (Raymakers et al . 2003). However, as you might guess, they've also been heavily over-fished and are rare to extinct in parts of this range (Wells 1997 and Raymakers et al . 2003).

Also like hippopus, the mantle of porcellanus, without exception, extends only to the upper margin of the shell. The exhalent siphon is also typically flattened and disc-like, forming a low cone with a circular opening, too. However, unlike hippopus, the inhalent siphon always has large, branching tentacles around it. The majority of these clams have a predominantly yellowish-brown or olive-green mantle with white to cream or golden splotches and/or thin stripes. Some may also be more grayish, though. They also commonly have areas of rather translucent tissue with little or no color.

The shell is white when clean, and its appearance is the origin of the common names. "China clam" refers to the look of the shell, not the country it hails from. And, while juveniles have shells that are commonly rather fan-shaped, with the hinge being about 1/2 its length, they do usually become slightly elongated as they get larger. The hinge becomes elongated, sometimes to 1/3 the length of the shell, and the shell also becomes moderately to strongly inflated. Like hippopus, porcellanus is often rather fat.

The shell also typically has 5 to 7 folds, with 5 or 6 being more developed. These are still usually quite low though, and there are no scutes on them, making their shells look similar to that of Tridacna derasa at times. So, despite being closely related species, porcellanus' shells can look quite different from those of hippopus.

The upper margin of each valve is usually topped by 5 or 6 smoothly rounded, inter-digitating projections, which are symmetrical to those on the other valve. This allows them to close themselves up very tightly when they want to. And, like hippopus, porcellanus typically maintains only a weak byssal attachment when possible, and only when young, living unattached when larger. Accordingly, the byssal opening is usually non-existent or very small for juveniles, being only a short slit at best, which becomes completely closed later. The area around their byssal opening also has numerous small, inter-digitating projections/teeth.

As far as size goes, Rosewater was the first to describe this species (1982), but according to Lucas (1988), he only had small species to examine. Lucas had access to larger specimens and reported a maximum size of 40cm.

Aquarium Care

With the basics covered, now we can get to caring for these species in aquaria, starting with water quality. The requirements for keeping these two clams (and the rest of the tridacnids, too) falls right in with what's considered "standard" for reef aquariums in general. Temperatures between 25° and 28°C are optimal, as is a pH of 8.1 to 8.3. Alkalinity should optimally be kept in the range of 9 to 12dKH , and calcium should be maintained at 380 to 450ppm, etc. About the only thing in particular to note is that as these clams grow, they add new shell material to the entire inner surface of the shell, not just the top edge. So, even a slow growing clam can use more calcium than you might expect, and having several in an aquarium can deplete calcium and alkalinity surprisingly quickly.

Other than that, having sufficient lighting is really the key to keeping them healthy. Light falling upon the soft mantle tissue and the symbiotic zooxanthellae harbored inside is the primary means by which all tridacnids get their energy in the wild, and the same goes for life in aquariums, too. So, you absolutely must give them sufficient lighting if you expect to keep them alive.

As mentioned above, both of these clams are not found at depths greater than 6m (about 20 feet). That's quite shallow compared to their Tridacna cousins, with the exception of Tridacna crocea . Crocea also lives from the intertidal zone to about 6m, but the rest of the species can be found significantly further down. For example, the popular T. maxima has been found at depths of 15m, and T. derasa at 25m. Obviously quite a difference.

What this means to hobbyists is that these two clams will need even more light than most other tridacnids in order to thrive. In my experience and based on information taken from the literature, which is covered in detail in Fatherree (2006), they can get by with less light than T. crocea , but their growth rate will be greatly reduced. Thus, even high-output fluorescent lighting will only suffice in relatively shallow tanks, or if a specimen is placed on the rockwork near the water's surface in a deeper tank. I would highly recommend squeezing as many bulbs into a canopy/fixture as possible at that, mounting the bulbs so that they are as close to the water as possible (without causing heat problems).

It's also important to note that there can be a great deal of variability between individuals of any given species of tridacnid. There are genetic differences that can make one clam more fit than another under the same conditions, two individuals may be carrying different strains of zooxanthellae, and so on. So, some specimens may be able to get by at times with less light than others, or further down in deeper tanks, but I implore you to not take chances.

With that said, experience has shown that metal halide lighting is really the way to go, preferably a combination system comprised of metal halide and fluorescent lighting. A standard 175w white to blue-white metal halide bulb should be sufficient for keeping these on the bottom of any small to medium size tanks, as in anything less than 45cm deep (or no deeper than this in a larger tank). But, I'd go ahead and move up to 250w, or even 400w bulbs if a specimen will be any further away from the surface, though.

Next, we get to whether or not you need to feed these in an aquarium. All tridacnids are filter-feeders that ingest a variety of particulates stripped from surrounding waters. However, their zooxanthellae can cover a great deal of their nutritional needs, and they're also able to absorb nutrients directly from seawater. In fact, if provided with enough light, tridacnids of any size can completely forgo the need to filter feed and can thrive in particulate-free water as long as there are enough dissolved nutrients present. I assure you that any claims to the contrary are false.

I dedicated an entire chapter to tridacnid nutrition in Fatherree (2006), which covers how they "work" in great detail, but I'll keep it simple here by saying that, in aquariums, basically everything is taken care of by having good lighting and simply feeding the fishes. Some fish food is left uneaten and becomes detritus, which tridacnids can filter out, and it also releases other nutrients into the water as it decomposes. But, most food is eaten by the fishes, which produce solid wastes that can also become detritus, and also give off dissolved nutrients that can be absorbed by a tridacnid, too. So, when you feed the fishes, you're feeding the clams, as well. For what it's worth, going all the way back to the early 90's, I've kept many tridacnids in well-stocked aquaria topped with metal halide lighting without providing any sort of particulate food whatsoever.

Still, the real question is about stocking levels, i.e. whether or not there are enough fishes in your aquarium/enough fish food going into you aquarium to support one or more clams. It is indeed possible to have too low a fish load (or too high a clam load depending on how you look at it) in a tank, which would mean that the amount of fish waste being produced would not be enough to support the needs of the clam(s). So, my advice is to refrain from taking any chances and use a quality phytoplankton product if you have any doubts. Basically, assuming water quality and lighting are sufficient, you should see shell growth if things are okay, while a lack of growth means they aren't.

You also need to think about water flow, as these two species live in shallow waters on reefs and near-reef environments that are regularly exposed to strong currents and wave activity. To the contrary, water movement in aquariums is typically nothing like that on the reef or nearby, as the flow in most aquariums tends to be quite linear and constant. While it's best to expose them to a low velocity surge and/or to turbulent flow, putting them in a position where a pump just blasts them with a strong, non-stop linear current is not recommended. Basically, any sort of current that causes a specimen to chronically retract its mantle and keep the shell even partially shut won't do. Thus, you can put one anywhere you like with respect to current, as long as it stays open fully.

Next, we get to placing these in the right spot. I think it's best to place any specimen of any sort on the same kind of substrate that you'd find it living on in its natural habitat, but this should be pretty easy since both of these can be found on sand, gravel, and coral rubble in the wild. So, these can be placed essentially anywhere in an aquarium, as long as lighting and current are acceptable.

Okay, with these things that you should do covered, now I'll run through some of the things that you should not do when it comes to the placement of a specimen. As is the case with any species of tridacnid, never place one in a tight crevice between rocks and such, as this may restrict their ability to open fully, and also increases the risk of them falling down into the rockwork if they move around too much. Never stick one in a hole in a rock that might restrict their ability to open fully, either. And, if you do place one in a large enough hole, never let a lot of detritus settle into the hole around the clam. If detritus does accumulate around one, you should blow it out regularly using a turkey baster or powerhead, etc.

Also, if a small specimen has attached itself to a sizeable piece of rock, shell, etc., never try to move the clam and the piece it's attached to by grabbing only the clam. That's a good way to injure the organ it uses to attach to such things, and you should always pick up the clam and the piece together and be very careful when handling the two. Likewise, you should never try to pull one off anything that it's attached to as you can rip the thread-producing byssal organ right out of it. And lastly, don't move a specimen repeatedly over a short period of time. It can be stressful enough trying to adapt to changes in lighting and current when they're moved into an aquarium, and quickly moving them from one place to another to another can be too much at times. Such activities can lead to slowed growth, a greater susceptibility to disease due to stress, or even outright kill them. If you must move one more than once, be sure to give it plenty of time between each move, as in a week or two at the least.

Well, that's all I've got. While you might never see a porcellanus for sale, there's always the chance you will, and hippopus is easy enough to acquire if you want one. So, keep all of this information in mind and do what it takes to keep them alive and well should you make a purchase.

References

1. Barnes, R. 1984. Morphogenesis of a nearshore windward fringing reef, Orpheus Island . Unpublished Honours Thesis, Department of Geography, James Cook University.
2. Fossa, S.A. and A.J. Nilsen. 2002. The Modern Coral Reef Aquarium, Volume 4 . Birgit Schmettkamp Velag, Bornheim, Germany. 480pp.
3. Govan, H. P.V. Nichols, and H. Tafea. 1988. Giant clam resource investigations in Solomon Islands. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific . ACIAR Monograph Number 9, Canberra. 274pp.
4. Delbeek, J.C. and J. Sprung. 1994. The Reef Aquarium: Volume One . Ricordea Publishing, Coconut Grove, FL. 544pp.
5. Fatherree, J.W. 2006. Giant Clams in the Sea and the Aquarium . Liquid Medium. Tampa, FL. 227pp.
6. Kinch, J. 2002. Giant clams: their status and trade in Milne Bay Province, Papau New Guinea. TRAFFIC Bulletin 19(2):1-9.
7. Knop, D. 1996 . Giant Clams: A Comprehensive Guide to the Identification and Care of Tridacnid Clams . Dahne Verlag, Ettlingen, Germany. 255pp.
8. Lucas, J.S. 1988. Giant clams: description, distribution, and life history. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific . ACIAR Monograph Number 9, Canberra. 274pp.
9. Pasaribu, B.P. 1988. Status of giant clams in Indonesia. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific . ACIAR Monograph Number 9, Canberra. 274pp.
10. Raymakers, C., S. Ringuet, N. Phoon, and G. Sant. 2003. Review of the exploitation of Tridacnidae in the South Pacific, Indonesia and Vietnam. TRAFFIC Bulletin, Brussels, Belgium.
11. Rosewater, J. 1965. The family Tridacnidae in the Indo-Pacific. Indo-Pacific Mollusca 1:347-396.
12. Rosewater, J. 1982. A new species of Hippopus (Bivalvia: Tridacnidae). Nautilus 96:3-6.
13. Shelley, C.C. 1988. Growth rates of Hippopus hippopus from Orpheus Island, Great Barrier Reef. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific . ACIAR Monograph Number 9, Canberra. 274pp.
14. Wells, S. 1997. Giant Clams: Status, Trade and Mariculture, and the Role of CITES in Management. IUCN - The World Conservation Union. Gland, Switzerland and Cambridge, UK. 77pp.

From time to time giant (tridacnid) clams will spawn in aquaria, ejecting clouds of sperm, and sometimes eggs, too. Usually this is a sign of excellent health, but it can also be a reaction to heavy stress. Unfortunately, such events won't lead to a tank full of baby clams, and can lead to real trouble in some cases, too. So, I thought I'd explain a bit about how tridacnids reproduce, why they spawn, and why it can be a problem. I'll also give you some advice on what to do if it happens in your tank.

Reproductive Biology

Tridacnids, like other clams, are broadcast spawners. This means that when it's time to reproduce, sexually mature clams will eject clouds of sperm and eggs into the water where they can mix with those of other nearby clams. I say sperm and eggs because fully mature tridacnids are both male and female at the same time, which means they are simultaneous hermaphrodites. Thus, they can make both and spawn both in the same event. They have to be fully mature to spawn both though, as tridacnids develop testes first with quite some time passing before they develop ovaries. So, sub-mature clams may spawn, but release only sperm.

Typically it's a relatively energetic act, as the shell and body contract vigorously making the sex cells spew quite far out of the smaller opening in a clam's fleshy mantle called the exhalent siphon. But, at other times these cells may just slowly sort of ooze out of the siphon and allow currents to do the rest (Alcazar 1988). Even a relatively small species, like Tridacna crocea, may release several million gametes (sex cells) at one time, but a big Tridacna gigas can cough out about half a billion! However, because their sperm have the ability to fertilize their own eggs, successful spawning requires a bit of timing, as self-fertilization is not a good thing.

Usually all of the sperm are released first, over a period of a several minutes, and requires numerous contractions of the body. There are typically only a few sperm coming out at first, but as a spawning event progresses, more and more will be ejected with each contraction, and then the amount will decrease with each contraction as the clam becomes spent. Then, as the sperm runs out, or maybe even quite a few minutes later, the eggs are released in the same manner. Just a few at first, with the numbers then increasing and later decreasing until the clam is spent again (although, again, many times no eggs are released at all). This works a lot better than releasing all of the gametes at the same time, as the sperm can be dispersed and moved away from the parent by currents before the eggs are released.

When spawning occurs, communicative substances are ejected with the gametes (spawn-inducing pheromones), and these can elicit spawning in other nearby clams, too. So, any tridacnids that are mature enough to produce gametes will start the same routine, releasing their millions of sperm and eggs into the mix with everyone else's. Thus, there's a much higher probability that there will be some genetic mixing within a population of neighboring clams. This may occur year-round near the equator, but it happens more often in the warmest times of the year in higher latitudes. There are numerous recorded exceptions though, as changes in temperature, salinity, lighting, and the tides may all play some part in the timing (Fitt & Trench 1981 and Trinidad-Roa 1988).

Regardless, when fertilization occurs, a new clam is only around 100µm in diameter, and within 12 hours or so the rapidly dividing mass of cells develops into what's called a trochophore larva (Ellis 1998). This is a free-swimming stage, when the miniscule larva can be carried along by currents to new localities. At this time there are rows of tiny hair-like cilia on the outside of the larva, which allows a larva to swim under its own power to some degree, as well.

After another 12 to 36 hours or so, a trochophore larva will pass into the veliger larval stage (Ellis 1998). A velum is a specialized organ that develops at this time, which is also covered by cilia and is used for locomotion, but also for feeding. So, it's during this phase that a larva can start to filter particles from the water. In fact, within the first 2 or 3 days, a clam typically has a well-developed velum, stomach, and intestines, and the shell is already forming, as well. It's fascinating to me that they can go from an egg to all that in a matter of a couple of days.

Timing can start to vary a great deal at this phase and through the rest of development though, as the developmental schedule varies from species to species, and on individual genetics, the condition of the gametes at spawning, and environmental conditions, too. After somewhere between 3 and 10 days, a veliger also develops a foot and is called a pediveliger ("ped" means foot) for some time (Ellis 1998). This foot is a muscular structure that can reach out and help the larva to move around on the bottom, and may also be used to collect food particles for a short time, as well (Reid & King 1988). It looks and acts almost like a sticky little tongue, and once formed, the larva will start to alternate between swimming around and crawling around on the bottom. The digestive system will continue to develop, as well, and so will the shell, while the larva moves about trying to find a suitable place to live. Then, once a spot in chosen, it'll settle down for the next step.

When the timing is right, which can be anywhere from 8 to 29 days after fertilization, the pediveliger will stop moving around and will begin to change into a juvenile clam (Ellis 1998). This change is appropriately called metamorphosis, and involves the atrophy and sloughing away of the velum and the loss of the cilia that were used for locomotion, too. After this, there is no more swimming about, and a post-metamorphic clam, for the most part, looks just like a tiny version of an adult, still being in the neighborhood of only 200µm (1/5 of 1mm) in size.

The gametes don't carry any zooxanthellae from their parents, so a clam must capture its own by filtering them from the water. This can start at the veliger stage at times, even before the specialized system of tubes that hold them in the fleshy mantle has started to develop, and when zooxanthellae are collected so early on, they're simply held in the stomach and stay there until after metamorphosis.

As a post-metamorphic juvenile develops, and the tubular holding system has begun to form, the zooxanthellae can typically be seen moving into the growing mantle within 2 to 7 days (Fitt & Trench 1981). Then they start to reproduce rapidly, while even more are being collected via filter-feeding, and they spread throughout the mantle in just 1 to 3 weeks. From this point on, a juvenile functions essentially the same as a small adult.

The clams that make it through metamorphosis to become juveniles typically grow at relatively slow rates at first. In fact, it may take them several months to make it to just a few millimeters in length. However, at some point their growth rate usually increases and continues at a faster pace until they approach sexual maturity and become adults themselves. Growth during this period, between the early parts of the juvenile phase and the mature phase of life, is also usually fairly linear, although things like changing environmental conditions, predation, disease, etc. can slow things down, of course.

As mentioned above, they don't become completely mature all at once, though. Depending on the species, an individual's genes, and the environmental conditions, a clam may become a fully-functioning male that can eject millions of sperm in as little as a couple of years, but may not become a functioning female for many more years after that (Lucas 1988). For example, Braley (1998) reported that it can take Tridacna gigas 4 to 5 years to become male-mature, and then another 5 to 6 years to become female-mature.

Many clams can become fully mature faster than this though, as Nash et al. (1988) reported that Tridacna gigas can become male-mature at 25 to 35cm, which is likely a year or so faster than Braley's observation of 4 to 5 years. And, Tridacna derasa can become female-mature by that size according to Adams et al. (1988), which is also in the 5-year range. Likewise, Heslinga (1993) said that Hippopus porcellanus could become a female-mature in four years, and Benzie (1993) said Hippopus hippopus could do it in only three. That's quite a difference in schedules.

Spawning in Aquaria

So, they do spawn in aquaria from time to time, but this can lead to serious trouble in the closed confines on a tank if you don't take immediate action. In fact, if the gametes aren't cleaned up quickly, there's a chance that a spawning event can lead to the death of everything in the tank! So, let's look at some of the things that might cause a clam to spawn (so that you can avoid them), and then what to do if it happens anyway.

First of all, spawning is a natural occurrence, thus healthy and mature tridacnids may spawn in aquariums as a normal part of life. However, they may also spawn if they're mature and are subjected to too much stress. When something goes wrong a clam may respond by ejecting any gametes it's holding, as this may ensure the survival of some of its potential offspring if it should be killed. Remember that tridacnids also give off spawn-inducing pheromones, too. So, if something entices a clam to spawn early, the rest of the clams in the area will likely do the same. In the wild, the gametes and fertilized eggs may be carried away by currents to other areas that have more favorable conditions, and the population's genes would stand a much better chance of survival if things went really bad for the parents.

Natural spawning will occur when a clam becomes ripe with large stores of gametes, but "survival spawning" as I call it, can occur at any time, whether a clam has only a few gametes or a full complement. It also doesn't matter if a clam is only at the male-phase of sexual maturity and can release only sperm, rather than both sperm and eggs, either. It's simply a last-ditch effort to save their genes, so whatever is there will be ejected, whether a clam is really ready to spawn or not.

The cues for something like this to occur can be wide-ranging, as essentially anything that over-stresses a clam can bring it on. A rapid change in temperature, up or down, can certainly do it. So can generally poor water quality, rapid changes in salinity, rapid over-illumination, predation or pestering, disease, physical damage, or anything else that's potentially life threatening.

In aquariums in particular, temperature change is likely the most common reason for survival spawning, but it can also happen after doing a really big water change rather than regular smaller changes. This can shock a clam due to some rapid fluctuation in water quality and possibly salinity, and adding too much freshwater at once to replace evaporated water can have the same effect, particularly in relatively small tanks (because it rapidly decreases salinity). Delbeek and Sprung (1994) also reported that adding a lot of new carbon can do it, as can waiting too long to replace old bulbs, both of which can lead to a rapid increase in light.

Of course, if something affects several clams in one tank simultaneously, then they may all spawn as a reaction to the environmental stress. However, if a single clam is suffering from an injury, disease, pestering, etc. it may undergo survival spawning, which can chemically trigger spawning in other clams, even if they aren't stressed. So, if you have more that one clam, having all of them spawn simultaneously doesn't necessarily mean that they are all stressed.

Now you might be thinking that survival spawning is a bad thing, but that a natural spawning in your aquarium by a healthy clam, or several, would be really neat. I remember bragging (to myself) about how great my own reef aquarium was and how healthy my clams were the first time this happened in one of my tanks, as it can certainly make you feel successful. However, I can assure you neither type of spawning is a good thing when it comes to the effects that they can have on a tank's water quality. As I said above, spawning can end up killing everything.

No, the gametes aren't toxic. In fact, they can be a very nutritious food source for many other things in an aquarium. Instead, the problem is that they'll all die in an aquarium and basically rot. They'll do it quickly, at that.

The gametes will start to die in about an hour, if not sooner, and because they all die and begin to decay relatively simultaneously, they can potentially cause oxygen levels in a tank to drop so low that all the fishes and other tank inhabitants may drop dead within a couple of hours. If eggs are released along with sperm and some of them are fertilized, they'll die too, due to the over abundance of sperm. In the wild, the gametes are immediately diluted into millions of gallons of seawater, but this obviously isn't going to happen in an aquarium. The problem is that when too many sperm try to fertilize a single egg, it kills that egg (it's called polyspermy). The precipitous drop in oxygen levels, when the gametes decay can also cause a spike in ammonia and nutrient concentrations, as well. That's bad too, as too much ammonia can also kill everything in an aquarium, and increased nutrient levels invariably lead to outbreaks of unwanted algae. Obviously, there's nothing good about any of that.

Of course, if something like a single 8cm male-mature Tridacna crocea spawns in a relatively large tank, it may not be a big deal. But, if larger clams spawn, or if a tank is small in size, you must take action immediately. The first thing to do is remove a spawning clam if at all possible. The clam can be temporarily placed into another container with some tank water, where it can release all of its gametes without fouling up the aquarium. If you have more than one clam, this may also prevent any others from joining in if you catch the first one in time.

Keep in mind that a clam may need to stay in the container for quite some time before it is completely spent, so you may need to pour out the water in the container and refill it a couple of times, and you should also add a powerhead pump or an air pump/airstone to keep oxygen levels up if possible. While this is going on, you should also make up a new batch of seawater to replace whatever you remove from the aquarium, too.

If the spawning clam(s) can't be removed, if possible, you can use a length of hose to create a siphon and suck up the gametes as they are being discharged. You can hold one end of the hose near the exhalent siphon of the clam, where the gametes are ejected, and run the other end to a bucket. However, instead of draining the whole tank while waiting for a clam to become spent, you'll need to hold your finger over one end of the hose to stop the flow of water, and only remove it and let the water flow when a pulse of gametes is released.

Likewise, you may be able to use a hose attached to a mechanical filter to suck the gametes up without removing water form the tank. I don't usually use cartridge-type filters on reef aquariums, but if you have one handy you can affix a hose to it and let the filter element collect the gametes. Of course, if you don't have a hose, you can just let such a filter run as it normally would, on the side of the tank or underneath it, too. But, it will take much longer to clear the water if the gametes aren't slurped up as quickly as they are released. Also note that the filter media should be cleaned out thoroughly afterwards, as the gametes will break down in it just as fast as they will in the tank.

Another method, described by Knop (1998), would be to use a pump and hose of some sort to collect the gametes and then direct the water through some form of perforated container filled with cotton or nylon wool. According to Knop, the gametes will stick to these materials due to a static charge, but I've never tried this myself.

Aside from these means of filtering out gametes, you should also do a substantial water change. I would say 25% for sure, and then see how things are looking. This will help to remove some of the remaining gametes, and can also reduce the concentration of ammonia if it has spiked. You should also test the water for ammonia afterwards if you are worried, and change even more water if you feel it is necessary.

Aeration in the tank should be increased in any way possible to keep oxygen levels up, from adding some airstones to positioning any powerheads that you have in such a way that they really make the water's surface roil. Many powerheads have little hose attachments that come with them, which can be used to blow large numbers of bubbles into the water, too.

Once everything is under control, it's also important to stop and think about what might have brought on the spawning event in the first place. If you feel that is was a natural, healthy event, then don't worry. However, if you feel that a clam(s) spawned due to stress, you need to try to determine the source of the stress and take action to correct the situation. Fortunately, if you can get things cleaned up, can figure out the reason a survival spawning event occurred, and then correct the situation, the clams that spawned will still have a good chance of recovering and everything else will be fine.

No Baby Clams

Lastly, I want to point out why you won't end up with a tank full of baby clams after a spawning event. Even under the best conditions, only a small percent of the eggs ejected in a spawning event will actually get fertilized, and of those that do, maybe 5% will make it through metamorphosis, or even far fewer than that. For example, Fitt & Trench (1981) reported that more than 95% of all the veligers in their study that had made it at least 3 days did not make it on through metamorphosis, regardless of the experimental conditions. This is due to microbial attacks for the most part, as the use of various antibiotics has been shown to greatly increase survival (Ellis 1998).

So, mortality can obviously be staggering when they're young, as thousands upon thousands succumb to microbial attacks and other problems. All those sperm, eggs (fertilized or not), veligers, etc. are also subject to being eaten by various filter-feeders and tiny predatory organisms, and then as they grow they may be eaten by crabs, worms, fishes, and myriad other critters, as well. Any sort of mechanical filtration would also strip them out of the water, as can a skimmer, and it's questionable that they could survive a trip through a powerhead or other pump. Polyspermy will ensure that few, if any, eggs would survive long in an aquarium, anyway. So, don't get too excited…

References

1. Adams, T.J.H., A.D. Lewis, and E. Ledua. 1988. Natural population dynamics of Tridacna derasa in relation to reef reseeding and mariculture. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
2. Alcazar, S.N. 1988. Spawning and early larval rearing of tridacnid clams in the Philippines. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
3. Benzie, J.A.H. 1993. Conservation of wild stocks: policies for the preservation of biodiversity. In: P. Munro (ed.) Genetic Aspects of Conservation and Cultivation of Giant Clams. ICLARM Conference Proceedings 39, Manilla. 47pp.
4. Braley, R.D. 1998. Report to GBRMPA on results of research done under marine parks permit no.G92/137. Aquasearch: http://www.aquasearch.net.au/aqua/long.htm
5. Delbeek, J.C. and J. Sprung. 1994. The Reef Aquarium: Volume One. Ricordea Publishing, Coconut Grove, FL. 544pp.
6. Ellis, S. 1998. Spawning and Early Larval Rearing of Giant Clams. Center for Tropical and Subtropical Aquaculture Publication 130. 55pp.
7. Fitt, W.K. and R.K. Trench. 1981. Spawning, development, and acquisition of zooxanthellae by Tridacna squamosa(Mollusca, Bivalvia). Biological Bulletin 161:213-235.
8. Heslinga, G.A. 1993. Palau (country report). In: P. Munro (ed.) Genetic aspects of conservation and cultivation of giant clams. ICLARM Conference Proceedings No. 39. 47pp.
9. Knop, D. 1998. Gamete release by giant clams in aquaria. Aquarium Frontiers: http://www.animalnetwork.com/fish2/aqfm/1998/may/shell/default.asp
10. Lucas, J.S. 1988. Giant clams: description, distribution, and life history. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
11. Nash, W.J., R.G. Pearson, and S.P. Westmore. 1988. A histological study of reproduction in the giant clam Tridacna gigasin the north-central Great Barrier Reef. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
12. Reid, R.G.B. and J.J. King. 1988. Postmetamorphic feeding in clams: relevance to Tridacnidae. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
13. Trinidad-Roa, M.J. 1988. Spawning and early larval rearing of giant clams in Pangasinan, Philippines. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.

Well, I wrote a book about tridacnid clams (Fatherree 2006a) and have been traveling around talking about them at club meetings and conferences for a couple of years now. I generally talk about providing them with sufficient lighting and whether or not they should be feed in aquariums, but I consistently get hit with the same story and questions wherever I go. With great regularity, someone tells me about losing a tridacnid, often one they've had for a while, for no apparent reason. And, of course, they want to know what happened to it. According to many of the stories, such losses often occur when everything else in a tank is fine (even other tridacnids), ruling out any general water quality problems. So, I call these cases "mysterious clam deaths."

With this in mind, I'd like to give you an overview of some of the things that can kill tridacnids, most of which aren't so mysterious. Many tridacnids fall due to stresses incurred from collection and shipping, but this would typically occur shortly after making it home, if they make it to a home. So, I won't spend any time on that. Instead, I want to go over things that, again, could cause a tridacnid to die after it has been in an aquarium for a longer period of time. For now I'll tell you that I get the impression that the majority of mysterious clam deaths are due to microbial or lighting issues, but we'll get to that momentarily.

First, I want to point out that, much to the dismay of clam keepers, in many cases there are no problem-specific symptoms of particular troubles. There are no treatments, or at least no easy treatments for many things, either. Instead, in so many instances, you may not know that anything at all is wrong with a tridacnid until it starts to gape open, and then it's usually too late to do anything to help it - even if there is some way to help it. Gaping simply means that a tridacnid's shell sits open, typically more than normal, but the mantle tissue is rather flaccid and not extended as far as normal (or at all), with the clam typically reacting sluggishly (or not at all) to any sort of stimuli.

This is indeed the number one sign of trouble, but it's also oftentimes the only obvious sign of trouble. Gaping can be brought on by just about anything that has negatively affected a tridacnid's health to the point that it is near death, which could be environmental trouble, such as poor water quality, or disease, such as a bacterial infection of some sort, or any number of other maladies. So, gaping is a sure sign of an impending death, but seeing it probably won't be of much help when it comes to deciding what, if anything, to do. Besides, after being in the hobby for the better part of 20 years, I don't recall a single incidence of a tridacnid recovering, despite any form of treatment, once it has reached a state of health so poor that it begins to gape.

And with that said, here's the list:

Bleaching

Tridacnids carry a complement of zooxanthellae, just as symbiotic corals do, and when conditions are unsuitable they can bleach out, just as symbiotic corals do. Basically, bleaching results from the loss of zooxanthellae and pigments in a tridacnid's mantle tissue causing it to lighten up in color. There are several things that can cause this to occur at some scale or another, but unacceptable increases in light intensity ("light shock") and/or temperature are the main culprits.

Tridacnids have several means to protect themselves from over-illumination and can adapt to increased lighting over time. However, if the amount of light, especially UV light, a tridacnid receives increases faster than it can adapt, the result is literally an overload of the photosynthetic process (Osmond 1981 and Asada & Takahashi 1987). Unacceptably high temperatures (and sometimes low) are also problematic and can have the same effect on photosynthetic systems.

However, despite its sometimes lethal effects, bleaching is not a cause of mysterious clam death, as it has obvious effects on the coloration of a clam, which anyone should notice. Patchiness can develop when it starts, and if the condition progresses a tridacnid will turn almost completely white. This often takes days, or even weeks, too. So, you'd definitely see it and it would be obvious that something's wrong. No mysterious deaths.

Predatory and Parasitic Snails

There are several species of snails in the genera Cymatium and Chicoreus that prey on tridacnids, some of which can grow as large as 10cm in length (Govan 1995). Most are smaller than this though, and can enter a tridacnid through the byssal opening, or can puncture the mantle by attacking from the shell margin or elsewhere when the shell is open, and then begin to eat a tridacnid's soft tissues. So, if you happen to spot a suspicious snail on the outside, or especially on the inside, of a tridacnid, you'll need to get rid of it immediately. Algae eating turbo snails, astraeas, conchs, and other well-known non-carnivores are fine, but I'd be wary of anything else. Fortunately, as far as I know these predators are not offered in the hobby, and I don't personally know of anyone that has lost a tridacnid to a predatory snail.

Conversely, a number of parasitic snails belonging to the genera Pyrgiscus, Turbonilla, and Tathrella, do kill tridacnids in aquaria with some regularity. These snails use a trunk-like snout called a proboscis to puncture a tridacnid's mantle near the shell margin and then feed on the victim's body fluids, and if too many attack a tridacnid, it can weaken or even kill it. These pyramidellid snails, better known as pyrams to hobbyists, are well-covered by Cumming (1988) and Boglio & Lucas (1997), but I'll give you the basics.

They reach a maximum size of just a few millimeters, are light colored, usually hide under a tridacnid or in the substrate during the day, and are thus very difficult to spot. So, you have to look very carefully for them, usually at night, if you can't remove a tridacnid to inspect it up close. They can also move from one clam to another if they choose, and they can reproduce very rapidly if left alone.

Once mature, these little snails will produce small, gelatinous, egg-filled globs on the shells of tridacnids every few days, which are transparent and particularly hard to spot. And from these globs can spring up to a couple of hundred offspring within just a few days. As if that's not bad enough, the offspring can feed on a clam, become sexually mature, and start to lay egg masses themselves in as little as a few weeks.

Without any natural predators to keep them in check in an aquarium, you can imagine how quickly a clam could succumb to their numbers. So, if pyrams or their egg masses are found on a clam, they must be scrubbed off with a stiff toothbrush immediately, and you should watch carefully for any signs of re-infestation. Of course, these could certainly lead to a mysterious clam death, as the snails and their eggs are hard to spot if you're not looking, and an infested clam will typically look fine until it gets so weak that it begins to gape. Note: You can find much more information about these snails and what to do about them online by taking a look at Fatherree (2006b).

Worms

There are several types of worms that may also pose a threat to the health to tridacnids. One of these is Urastoma cyprinae, better known as the oyster gill-worm, which is a type of turbellarian flatworm. These small worms are sometimes found in the mantle cavity, often on the gills, and in the digestive tract of Tridacna gigas and T. maxima, as reported by Goggin & Cannon (1989). However, they don't seem to have any adverse affects on the health of these clams in the wild. Still, in a closed aquarium system and/or under stressful conditions, I'd imagine they may become problematic. Humphrey et al. (1987) reported that some clams carried an unidentified turbellarian flatworm and the nematode roundworm Syringolaimus, but no specific problems were mentioned. So, yet again, they may not be anything to worry about in the sea, but they may also become a problem in aquariums. And, Newman et al. (1993) reported consistently finding the polyclad flatworm Stylochus matatasi associated with the death of Tridacna gigas in one study of clam mortalities, which, unlike the others, may actually be large enough to see, as they can reach a full size of about 6cm. However, while they may be spotted at times on the mantle, they can also do their damage inside the mantle cavity where you more than likely wouldn't spot them until after a clam is dead and removed. So, again, any of these may have the potential to cause a mysterious clam death, as there no distinctive symptoms will appear until a clam is weakened to the point of gaping.

There are also a number of errant polychaetes, commonly known as bristle worms, which have the potential to kill a clam. A few can get ridiculously large, with a handful of species reaching lengths of one or more meters, and some are indeed carnivorous. However, these relatively large and potentially dangerous species are actually very, very uncommon in aquariums, and they represent only a tiny percent of the hundreds of species of bristle worms that can be found in the seas. To the contrary, the overwhelming majority of species are quite harmless, and are actually beneficial in aquariums, as many are scavengers and/or detritus eaters.

However, there is the remote possibility that you may unintentionally introduce a carnivorous species to your tank, maybe hidden in a piece of live rock, so you should watch out for any worm that is obviously attacking a tridacnid. Likewise, there is at least one species (Oenone fulgida) that can apparently bore a hole through a clam's shell and then chew on its tissues (Delbeek & Sprung 1994), so watch out for anything like that, too. It shouldn't be difficult to spot, as this worm may be only about 2.5mm in diameter, but can reach a length of around 30cm and is bright orange in color.

Still, I personally have never seen any evidence whatsoever of a bristle worm attacking a healthy clam in any way. Yet what I have seen is scavenging worms coming out and feeding on the tissues of a very unhealthy or dead clam. So, if you happen to lose a tridacnid and then discover that there are some bristle worms crawling around inside it, don't assume that the worms were the cause of death. In other words, there's a chance that a mysterious clam death may be brought about by a hungry bristle worm, but it's a slim chance.

Microbial Problems

A tremendous number of bacteria are found in seawater, but they typically aren't a problem for healthy tridacnids. However, if a clam is stressed and its ability to defend itself is reduced, these same bacteria can become deadly. And, to make matters worse, bacterial populations can be much larger in aquariums, as they are closed systems with relatively high nutrient levels. In fact, Fitt et al. (1992) wrote that even small amounts of organic material added to seawater can lead to a 1000-fold increase in bacterial populations within a matter of hours in some situations. Thus, anything from excessive changes in temperature, salinity, lighting, etc., or something like a physical injury (like damage to the byssal organ during a relocation or a nip from a fish, for example) can compromise a clam's immune system and in turn lead to a quick death in an aquarium.

Humphrey et al. (1987) listed off quite a few of these potentially dangerous bacteria, including various species of Vibrio, Acinetobacter, Enterobacter, and Pseudomonas, and Knop (1996) added Xeromonas and Plesoimonas, too. Then there's a rickettsiales-like bacteria, that forms cysts on the gills of Hippopus hippopus, which was reported by Norton et al. (1993a), and an unidentified bacteria found on the gills of Tridacna gigas, reported by Norton et al. (1993b), too. Apparently any of these have the ability to kill a clam, and again, the only symptom of trouble that you might see is gaping, and possibly some necrotic mantle tissue.

Likewise, a protozoan by the name of Perkinsus olseni has been found in the digestive tract of Tridacna crocea, T. maxima, and T. gigas (Goggin & Lester 1987 and Goggin 1996), which can possibly lead to a clam's death. But, as you'd expect by now, there are no diagnostic symptoms that you can identify, and there's no recommended treatment even if you could.

An unidentified protozoan was also found along with Perkinsus in dead and dying specimens of Tridacna maxima, T. gigas, and Hippopus hippopus in some areas of the Great Barrier Reef and reported by Alder & Braley (1988). They were looking for the possible cause(s) of a great number of relatively sudden deaths of many clams when they found these two protozoans, but could not determine if one or both were the actual cause of the deaths. There were no specific symptoms of trouble in this case either, as the only indication that something was wrong was the death of the clams.

Marteilia spp. is a protozoan known to attack the digestive tract of oysters, and Norton et al. (1993c) reported a Marteilia-like protozoan that attacked the kidneys of Tridacna maxima, too. Again, there are no outwards symptoms of trouble, infection can lead to death, and there is no recommended treatment.

Another unidentified protozoan has also been found in the blood of many specimens of Tridacna crocea, as reported by Nakayama et al. (1998). In fact, in one survey they found it present in 77 of 99 clams tested. They didn't report any noteworthy effects, but the things are still there and I would guess they could become a problem in some situations.

And, yet another unidentified protozoan can invade the mantle tissue of Tridacna gigas and consume the zooxanthellae according to Humphrey (1988). However, its effects are poorly understood, too.

Knop (1996) also reported that an unidentified protozoan similar to Perkinsus was reported to attack Tridacna crocea, T. maxima, and T. squamosa. The organism produced small white cysts on the upper and lower surfaces of the mantle and around the byssal opening, and was 100% fatal when left untreated. So, this one actually has signs of trouble that you can see, and Knop gave it the appropriate name "whitespot disease". Unfortunately, it is also apparently very contagious and leads to death in a few weeks to a few months time.

However, there is one disease called "pinched mantle" that can be easily recognized, which is also thought to be caused by yet another unidentified protozoan (Barry Neigut, pers. comm.). This condition can be spotted when the smooth, curving edges of the mantle are pinched and contorted. The clam may look like it is doing its best to stretch out the mantle tissue, but the margins just won't extend fully the way they should. So, this wouldn't be mysterious, either.

According to Neigut, it affects Tridacna crocea most often, with the other species being more resistant, but not immune. And, it can spread to other clams at times, being nearly 100% fatal, usually within a week or two of the first signs. Pinched mantle can be treated by giving an infected clam a freshwater dip for approximately 30 minutes, and Neigut has had good results with the use of the medication metronidazole, too. Note: You can also find much more information about pinched mantle and what to do about it online by taking a look at Fatherree (2006b).

As far as what's in the scientific literature that can affect tridacnids, that's all I can find regarding microbes. However, it's important to note that there may be many, many more sorts of things from viruses, to bacteria, to worms that might affect tridacnids. Again, I haven't found anything other than what I've presented above, but you can take a look at numerous sources, such as Paillard et al. (2004), Bower (2001), Bower & McGladdery (2001), Hine & Thorne (2000) and Dungan et al. (1989), and see just how many known infectious diseases and parasites affect various other sorts of clams. Many clams that are aquacultured for food have been given far more attention than tridacnids have, and after seeing all of the things that researches have come up with that affect food clams, I can't help but think that tridacnids likely have far more tiny enemies than have been documented.

Lighting Problems

Corals are particularly simple as far as animals go, and they require relatively few calories to get through the day. On the other hand, tridacnids have a complete digestive system, gills, kidneys, a heart, blood, etc. and burn up much, much more energy than corals. So, many tridacnids require more light than many corals do. Each species of giant clam is different though, and some certainly need more light than others in order to thrive. For example, Tridacna crocea is found only in very shallow waters in the wild and needs more light than the other tridacnid species. In fact, I'm quite certain I've never seen one living more than about 10 feet down. Conversely, I've found numerous specimens of T. gigas and T. squamosa living at well more than twice that depth, and T. derasa can often be found living even deeper. Regardless, don't make the mistake of automatically thinking that if a given lighting system is bright enough to keep various types of corals alive and well that it's also automatically bright enough to keep various types of tridacnids alive and well. Maybe it's not.

Personal experience and the stories of others' have convinced me that there's a great deal of variability amongst clams of the same species when it comes to lighting needs, too. In other words, if a given lighting system is bright enough to keep one specimen of Tridacna crocea alive, that doesn't necessarily mean it's bright enough for all specimens of T. crocea. In any given batch of T. crocea, there will be some that grow faster than the others, some that get bigger than others, some that are more resistant to bleaching/disease than the others, some that are more brightly colored the others, and some that can thrive under less light than the others. Get the idea? It's simply due to genetic diversity within the species, and that's the reason that I generally make a conservative recommendation of placing any specimen of any species under intense metal halide lighting, a lot of high-output fluorescent bulbs, or something comparable like a good L.E.D. fixture.

With that said, it's time to say that I think the vast majority of mysterious clam deaths are simply due to insufficient lighting. Certainly not all cases, but most of them. The problem is that too many hobbyists do exactly what I warned against above. They have a lighting system that seems to be perfectly fine for keeping a number of corals, so they assume they can add in a tridacnid, too. Unfortunately, Tridacna crocea, the most light-demanding of the bunch, is also often the most attractive choice, and most often picked, at that. Then the clam slowly begins to starve.

The bad part is that it can take several weeks or even a few months for a tridacnid to finally starve to death, and they'll typically look just fine until they have reached the point of no return and start gaping. This is why so many hobbyists tell the same story, that their corals are fine, but their clam looked great for some months, and then up and died for no apparent reason - mysteriously. In reality, the deceased may have been in the process of dying since the day it was put in the tank. Look at it this way, if a specimen is getting 95% of the light it needs, then it won't just croak overnight. Instead, it will very slowly waste away. Of course, if it's getting only 5% of what it needs, then yes, it may take only a few days before problems start.

On many occasions I've talked to hobbyists that have lost a tridacnid, and a few times have seen their tank and the shell of the deceased, and one thing keeps coming up - a lack of growth. In so many cases, I learned that while corals and such were growing fine in the same tank, the clam extended its mantle and looked normal (no signs of pinched mantle, bleaching, etc.) but never grew at all. And in just about all of these cases, I also find that they have relatively low-output lighting for a reef aquarium.

The key to preventing such a death is to regularly look for new shell growth. Assuming water quality is where it should be and that other skeleton-building organisms are thriving, if a tridacnid is not adding on new material to the edge of its shell, there's a problem. While there are uncommon specimens that have a yellowish/orangish/pinkish shell margin, the overwhelming majority should have a clean white one. It should never look "dirty", greenish, brownish, etc., which is the result of a lack of shell growth and the encroachment of algae right up to the mantle. In fact, small to medium-sized clams of any species should have a clearly visible clean white band of new shell material all the way around the shell margin, as they typically have much higher growth rates than larger, older clams. So, if you don't see a clean white shell margin and a clean band of new shell material on a small to medium-sized specimen, the problem is very likely insufficient lighting, and it'll need to be moved up closer to the lights, taken out of the tank, or rescued with a new lighting system.

References/Sources for More Information

1. Alder, J. and R.D. Braley. 1988. Mass mortalities of giant clams on the Great Barrier Reef. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
2. Asada, K. and M. Takahashi. 1987. Production and scavenging of active oxygen in photosynthesis. In: Kyle, D.J., C.B. Osmond, and C.J. Arntzen (eds.) Photoinhibition. Elsevier, Amsterdam. 307pp.
3. Boglio, E. and J.S. Lucas. 1997. Impacts of ectoparasitic gastropods on growth, survival, and physiology of juvenile giant clams (Tridacna gigas), including a simulation model of mortality and reduced growth rate. Aquaculture 150: 25-43.
4. Bower, S.M. 2001. Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Hinge Ligament Disease of Juvenile Oysters: http://www-sci.pac.dfo-mpo.gc.ca/shelldis/pages/hldjoy_e.htm
5. Bower, S.M. and S.E. McGladdery. 2001. Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Table of Contents: http://www-sci.pac.dfo-mpo.gc.ca/shelldis/toc_e.htm
6. Cumming, R.L. 1988. Pyramidellid parasites in giant clam mariculture systems. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
7. Delbeek, J.C. and J. Sprung. 1994. The Reef Aquarium: Volume One. Ricordea Publishing, Coconut Grove, FL. 544pp.
8. Dungan, C.F., R.A. Elston, and M.H. Schiewe. 1989. Evidence for colonization and destruction of hinge ligaments in cultured juvenile Pacific oysters (Crassostrea gigas) by cytophaga-like bacteria. Applied Environmental Microbiology 55(5):1128-1135.
9. Fatherree, J.W. 2006a. Giant Clams in the Sea and the Aquarium. Liquid Medium, Tampa. 227pp.
10. Fatherree, J.W. 2006b. Troubles with Tridacnids: a Look at Two Common Problems. Reefkeeping: www.reefkeeping.com/issues/2006-09/jf/index.php
11. Fitt, W.K., G.A. Heslinga, and T.C. Watson. 1992. Use of antibiotics in the mariculture of giant clams (F. Tridacnidae). Aquaculture 104:1-10.
12. Goggin, C.L. 1996. Effect of Perkinsus olseni (Protozoa, Apicomplexa) on the weight of Tridacna crocea (Mollusca, Bivalvia) from Lizard Island, Great Barrier Reef. Aquaculture 141:25-30.
13. Goggin, C. L. and R.J.G. Lester. 1987. Occurrence of Perkinsus species (Protozoa, Apicomplexa) in bivalves from the Great Barrier Reef. Diseases of Aquatic Organisms 3:113-117.
14. Goggin, C.L. and L.R.G. Cannon. 1989. Occurrence of a turbellarian from Australian tridacnid clams. International Journal for Parasitology 19:345-346.
15. Govan, H. 1995. Cymatium muricinum and other ranellid gastropods: major predators of cultured tridacnid clams. ICLARM Technical Report 49, ICLARM, Manila, 136pp.
16. Hine, P.M. and T. Thorne. 2000. A survey of some parasites and diseases of several species of bivalve mollusc in northern Western Australia. Diseases of Aquatic Organisms, 40.
17. Humphrey, J.D. 1988. Disease risks associated with translocation of shellfish, with special reference to the giant clam Tridacna gigas. In: Copeland, J.W. and J.S. Lucas (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Number 9, Canberra. 274pp.
18. Humphrey, J.D., N. Gudkovs, and J.S. Langdon. 1987. Report on Health Certification of Cultured Giant Clams Tridacna gigas Proposed for Export. Australian Fish Health Reference Laboratory. Geelong, Australia. 13pp.
19. Knop, D. 1996. Giant Clams: A Comprehensive Guide to the Identification and Care of Tridacnid Clams. Dahne Verlag, Ettlingen, Germany. 255pp.
20. Nakayama, K., M. Nishijima, and T. Maruyama. 1998. Parasitism by a protozoan in the hemolymph of the giant clam, Tridacna crocea. Journal of Invertebrate Pathology 71:193-198.
21. Neigut, B. 2005. Owner of Clams Direct. personal communication.
22. Newman, L.J., L.R.G. Cannon, and H. Govan. 1993. Stylochus (Imogene) matatasi n. sp. (Platyhelminthes, Polycladida): pest of cultured giant clams and pearl oysters from Solomon Islands. Hydrobiologia 257(3):185-189.
23. Norton, J.H., M.A. Shepherd, M.R. Abdon-Naguit, and S. Lindsay. 1993a. Mortalities in the giant clam Hippopus hippopus associated with Rickettsiales-like organisms. Journal of Invertebrate Pathology 62:207-209.
24. Norton, J.H., M.A. Shepherd, and H.C. Prior. 1993b. Intercellular bacteria associated with winter mortality in juvenile giant clams, Tridacna gigas. Journal of Invertebrate Pathology 62:204-206.
25. Norton, J.H., F.P. Perkins, and E. Ledua. 1993c. Marteilia-like infection in a giant clam, Tridacna maxima, in Fiji. Journal of Invertebrate Pathology 61:328-330.
26. Osmond, C.B. 1981. Photorespiration and photoinhibition; some implications for the energetics of photosynthesis. Biochemica Biophysica Acta 639:77-98.
27. Paillard, C., F. Le Roux, and J.J. Borrego. 2004. Bacterial disease in marine bivalves, a review of recent studies: Trends and evolution. Aquatic Living Resources, 17.

I first would like to thank the Advanced Aquarist's staff for all their hard work in creating a first class online magazine. What a benefit it is for us "regular folk" in this great hobby to have a place like this, that with just a few mouse clicks we can access so much valuable information. When Wade invited me to have my reef featured I felt honored yet a little hesitant. I was a little worried my aquarium may not be quite up to the standard people might expect but then thought it's not always about where you are right now but where and what you are striving to be. I hope that through my photos and remarks you will be able to feel the passion I have for this hobby and get a sense of the enjoyment I receive from it. I have always been fascinated with the ocean and diverse life forms we find there. It truly is another world and I love this hobby that allows us to keep a small part of it in our homes. I am grateful to be given this opportunity to share my little piece of the ocean with you.

History & Tank Profile

I ran freshwater aquariums for years, African cichlids mainly and like many people seldom had less that two tanks going at any given time. When I shut my last one down in the late 1980's due to a leak I decided at that time that when I eventually got back into the hobby I would switch to salt water. In October 2004 that dream became a realization when I had a tank custom built. I thought I would begin my salt water adventure with a FOWLR and maybe add in a few soft corals to sway back and forth in the flow. I had seen this kind of display at some fish stores and thought they looked pretty cool. Within about four months I found I was actually buying coral as often as fish and my tank slowly started to become a reef. By spring 2005 I was up to about 24 fish, an RBTA, several LPS with a few leathers and mushrooms as well as some Montipora caps and digitata. My original lighting was a 72" Power Compact fixture which I thought was pretty bright and assumed it was all I would ever need. However, by the summer 2005 I knew I wanted to upgrade to Metal Halides so I could add in some so called "harder to keep" sps coral such as acropora. In July 2005 I upgraded to a 72" fixture with 3x175 watt & 2x 96 watt PC actinics. In September 2005 I added a sump and Dec 05 upgraded my protein skimmer. I once again figured I was all set. Then in summer 06 I added in an RO/DI unit with an auto top-off going to the sump. I finally switched to R/O because I had a major hair algae outbreak that almost killed my reef. It got so bad that I did a complete tear-down in September 2006 and was rethinking whether or not to even stay in the hobby. I obviously kept going which is a decision I am pleased I made. It turns out that my skimmer was running at about 1/3 capacity for several months which sent my nitrates through the roof. I fixed the skimmer which worked fine for awhile. Right after the skimmer ordeal my main ballast went in my light fixture so I was again at a crossroads. It helped me realize my reef wasn't where I wanted it to be anyway, so in October 2006 I once again upgraded my lighting. I decided on a 72" fixture that houses five HQI bulbs, two 150 watt 20 K and three 250 watt 10 K, that would allow me to create a better sunrise and sunset effect with a higher intensity and then added in some moon lights for extra effect. I have since added a T5 fixture to supplement the lighting to help give that little extra pizazz I had been looking for. Now I was closer to the intensity I wanted but the water was getting too hot. I decided after loosing many sps colonies from the heat that I needed a chiller. After installing the chiller I still questioned why it had to keep running so often to keep things cool, I mean my light was hot but not that hot. Anyway, I did some checking and discovered I had a faulty heater that was staying on 24/7 and this had likely been my biggest problem all along. That said the chiller is still a definite necessity and really helps keep the water temperature stable. Around that same time I also changed out the powerheads to Tunze's with a multi-controller. The difference in the flow and random surge has made a huge difference in keeping my reef happy and growing.

In November 2006 I connected what had been my acrylic 40 gallon cichlid aquarium in-line to use as an ornamental Refugium & Softie tank. The refugium is made up of live rock, soft corals, and macro-algae. This tank has an "old school" sump in the rear where I also keep a "cheato chamber" running on a reverse photo period. I have since added in a 40 gallon frag propagation tank. This has increased my water capacity to approximately 250 gallons. This extra volume along with the increased nutrient exportation has made a huge difference in helping to stabilize the system as well as virtually eliminate nuisance algae growth in the display. Adding more volume to the system meant more water draining to the sump in case of a power failure. Since it will only hold the amount of water that drains from the main display I drilled the sump wall and added an emergency overflow going to a 10 gallon tank. Fortunately, I haven't needed it so far but I am sure the day will come and it helps give some peace of mind against flooding. As you can see the last two years, have been a "reefer's roller coaster ride." It seems whenever my reef starts to do well "Murphy's law" kicks in and something else happens. The summer of 2007 was to be no different. I discovered our dishwasher located in the kitchen, on the floor directly above where the tank is, had been leaking and dripping straight into the tank for an undetermined amount of time. The drain hose had sprung a leak and who knows what chemicals ended up in the tank between the soapy dish water and the basement ceiling tiles, etc. Needless to say I took immediate action. I changed and added extra carbon and did seven water changes in eight days of 15% each and managed to save the majority of livestock but the SPS took a big hit. Most of it lived although I did I loose several nice pieces. Unfortunately what did live either bleached or browned out, but for the most part over the last six months it has bounced back quite nicely. There are still a few pieces I am patiently waiting on to color back up but my hopes are high. Bad things seem to happen in waves, so of course while the dishwasher incident was occurring my skimmer had also quit working. I was without a skimmer for most of the summer and in late August 2007, I upgraded to a much bigger unit that could handle the load. I was very fortunate to not have a huge algae bloom and I give Polyp-labs a lot of credit for keeping my nitrates under control as I kept dosing with "reef-resh" during that time. The new skimmer has a 24 inch footprint and is 30" tall so I had to install it away from the main display as there was no room for it. I modified the skimmer to drain into a 5 gallon bucket both as a help for emptying skim mate because it's inconveniently located under the frag tank and as a safe guard against it overflowing. No good sps drama would be complete without having a few "red bug" battles so I of course have had run ins with them and learned the hard way that nothing goes into the system without being given a dip for such pests. I have been lucky so far and never had acropora eating flatworms. Anyway, things have been pretty stable since then so I am keeping my fingers crossed and keep "knocking on wood" that this present trend will continue.

Tank Specifications

• Main Display - 130 gallon ½" glass euro-braced, 72"Wide x 18"Deep x 24" High.
• Refugium - 45 gallon acrylic hex front with built in rear sump (old school), 48" Wide x 18: Deep x 24" High
• Frag Prop tank - 40 gallon euro-braced
• Sump - 30 gallon acrylic

Water Parameters:

• Temp - 27 C / 79-80 F
• SG - 1.026
• pH - 8.2
• Ammonia - undetectable
• Nitrates - undetectable
• Calcium - 440 ppm
• Alk - 8 DKH
• Mag - 1350 - 1400 ppm

Equipment

• Return Pumps - Ocean Runner 6500 - Ocean Runner 3500 (return for frag tank)
• Protein Skimmer - Euro-Reef RC500
• Skimmer Pumps - 3x Eheim 1262
• Chiller - Aqua Medic AT5000
• Lighting Fixtures - Aqua Medic "Sexy" Ocean Light (all HQI) - Aqua Medic T5 fixture 72"
• Bulbs - Aqualine 3 x 250 watt 10k & 2x 150 watt 20k - T5's Koralen Zucht 4x 39 watt Fiji Purple
• Moon Lights - 2x 1 watt LED (blue)
• Powerheads - 2x maxi-jet (for additional flow in behind the rock work), Seio 820, Hydor Koralia #4, Tunze Nanostream 6045, Tunze Turbelle Stream 1x 6000 & 1x 6100 with Tunze 7095 Multi Controller (with single white LED moon phase light)
• Refugium Lighting - 2x 96 watt Power Compact 2x 96 watt Actinic Power Compact
• Filters - 100 micron pre-filter socks installed in sump beneath tank's overflow and on the skimmer return to improve water clarity and bubble control
• Heater - 200 watt titanium heater with Aqua Medic Temperature Controller
• RO/DI - Coralife 3 stage with pump
• F/W Reservoir - 45 gallon container aerated 24/7 to maintain PH level
• Top-Off Unit - Aqua Medic SP3000 Single Dosing Pump

Husbandry

In January 2007 I started running the Polyp-Labs "Reef-Fresh" program which helps keep the nitrate levels in check using bacterial strains, amino acids and other supplements. It is said to give results similar to Zeovit, basically encouraging a low nutrient environment. I have been pleased with the results over this past year or so.

I use Randy Holmes Farley's 2 part recipe for dosing Calcium & Alkalinity. My reef has a demand which requires almost 500 ML of each on a daily basis to keep the levels stable. Magnesium is added at approximately 500 ML per week as per Randy's recipe. Potasium is also dosed daily while other trace elements such as Iodine & Strontium are dosed biweekly.

Routine Maintenance:

• Skimmer - empty & clean twice a week
• Pre-Filter bags - change twice a week
• Carbon - change out monthly (media bag runs through an Aquaclear filter in the refugium)
• Water Changes - 10-15% monthly
• Prune & frag corals - as needed

Lighting Schedule:

Main Display:

• 8:00 AM -1 watt moonlights on 10:30 AM - moonlight off
• 9:00 AM - T5's on 9:30 PM - T5's off
• 10:00AM - 150 watt 20k m/h on 10:30 PM - 150 20k's off
• 12:00 PM - 250 watt 10k m/h on 8:30 PM - 250 10k's off
• 10:45 PM - 1 watt moonlights on 12:00 AM - moonlights off
• white led moon phase light runs automatically via sensor while main lights are out

NOTE: I try to time the photo period in a way in which I can spend more time on the reef while it's active. By starting the lights a little later in the day they are on for a longer time after I get home from work which gives me more time to tinker and enjoy.

Refugium/Softie Tank

• 40 watt light on reverse photo period in the rear sump "Cheato chamber"
• 8:00 AM -actinics on 11:00 PM - actinics off
• 9:00 AM - pc's on 10:00 PM - pc's off
• Frag Tank (250 watt Geisman HQI pendent)
• 9:00 AM - on 9:00 PM - off

Feeding Schedule:

Feeding is provided on a daily basis, generally twice per day, and food is alternated to give their diet a variety of flakes, pellets, brine(super)shrimp, mysis shrimp, cyclopeze and "nori" seaweed. I also mix in some "Reef-roids" or similar product, on occasion to provide some extra food for the corals.

Livestock

Fish & Inverts

Main Display

• 1-scooter blenny
• 1-yellow tang
• 1-blue tang
• 1-naso tang
• 1-chevron tang
• 1-coral beauty angel
• 1-royal gramma
• 1-bi-colour blenny
• 1-yellow tail damsel
• 1-4 stripe damsel
• 3-green chromis
• 2-black & white ocileris clowns
• 1-blue devil damsel
• 2-watchman gobies
• 1-niger trigger
• 1-black brittle star
• 1- Nardoa novaecaledoniae star
• 1 - yellow coris wrasse
• Foxface rabbit fish
• 1-Blood Red hawkfish
• 1-longnose hawkfish
• 1-red serpent star
• Hermit crabs
• 2-conches
• Snails (Too hard to put a number on)
• 1-Entacmaea quadricolor (Green bubble tip anemone)
• 5-hawaiian feather dusters

Refugium/Softie tank

• 1-flame angel
• 2-skunk cleaner shrimp
• 1-yellow clown goby
• 1-marine beta
• 1-purple fire fish
• 1-blue striped pipefish
• 2-orchid dottyback
• 1-pencil urchin

Frag prop tank

• 2-banggai cardinals
• 3-fairy wrasses
• 1-potters angel
• 1-sailfin tang
• 1-rabbitfish
• 1-watchman gobie
• 1-fire shrimp
• 1-sea cucumber

Clams

• 5-Tridacna crocea
• 1-Gigis
• 1-Tridacna maxima

Live Rock

Approximately 400 Lbs containing a mixture from: Australia, Fiji, Jakarta, Vanuatu, Caribbean & Belize, Hawaii, Mexico & Tonga.

Coral

I don't know all the proper names of many of the corals in my collection so I will only list those that I have identified through research and/or a lot of help from others in the hobby who are more knowledgeable than me. Identification can sometimes be tough when trying to compare an aquarium coral with a picture of one in the wild from a book, especially when you enter reticulate evolution into the equation. With some acropora, I find that I often know what species they aren't but can't always tell exactly which species they are, at least while they're alive. Anyway, I have tried to list the corals by the general taxonomic family first and then by genus and species.

Scleractinian (stony) Corals

Small Polyp Scleractinia

Acropora

A.Loripes, A.Lovelli, A.Rosaria, A.Nana, A.Verweyi, A.Hoeksemai, A.Microphthalma, A.Humilus, A.Gemifera, A.Caroliniana, A.Jacquelineae, A.Prolifera, A.Loisetteae, A.Prostrata, A.Youngei, A.Austera, A.Tortousa, A.Valida, A.Proximalis, A.Millepora, A.Aspera, A.Kimbeensis, A.Batunai, A.Formosa, A.Tenuis, A.Turaki, A.Lokani, A.Horrida, A.Abrotanoides, A.Robusta, AAbrolhosensis, AStriata, A.Pichoni, A.Efflorescens, A.Plana, A.Pulchra, A.Subulata, A.Aculeus, A.Insignis, A.Maryae, A.Cerealis, A.Echinata, A.Bifurcata, A.Convexa, A.Chesterfieldensis, A.Divaricata, A.Hyacinthus, A.Convexa, etc.

Pocilloporidae

Pocillopora Damicornis, Pocillopora Verrucosa, Stylophora Pistillata, Stylophora Subseriata, Seriatopora Hystrix, Seiatopora Caliendrum, Seriatopora Stellata.

Montipora

M.Digitata, M.Capricornis, M.Danae, M.Verrucosa, M.Capitata, M.Confusa, M.Samarensis, M.Flabellata, M.Tuberculosa, M.Aequituberculata, M.Undata, M.Setosa, etc.

Misc SPS.

Hydnophora Pilosa, HydnophoraRigida, Porites sp., Merulina Scabricula, etc.

Large Polyp Scleractinia

Lobophyllia sp, Symphyllia sp, Caulastrea Furcata, Echinopora sp, Favia Speciosa, Trachyphyllia Geoffroyl, Euphyllia Ancora, Euphyllia Divisa, Turbinaria Peltata, Acanthastrea Lordhowensis, Acanthastrea Echinata, Turbinaria Reniformis, Echinophyllia Aspera, Mycedium Elephantotus, Oulophylia sp, Duncanopsammia Axifuga, etc.

Soft Corals

Corallimorpharians (mushroom corals)

Rhodactis, Actinoddiscus (=Discosoma) Striata, Mutabilis, Cardinalis, etc.

Octocorals

Tubipora Musica, Xenia sp. , Alcyonium, Lobophytum Pauciflorum, Sarcophyton Elegans, Sinularia Notanda, Sinularia Dura, Capnella Imbricata, Heliopora Coerulea, etc.

Gorgonians

Briareum Asbestiumi, Rumphella

Zoanthids (Various species)

Pachyclavularia Violacea (green star polyps)

A Few Comments I've heard:

In Michael Paletta's book "Ultimate Marine Aquariums" he asks his subjects about some of their favorite remarks people make when they see their reefs. I hope he won't mind me borrowing his idea as I thought it's a good one and I often get a kick out of people's reactions when they see my reef for the first time. Here are just a few first time comments:

• Oh my gosh, I've never seen anything like this before.
• Is that salt water? Is all that stuff alive? Are those plants? They're all corals? Even those? Are they real? How did you get them?
• Do you bring these back when you go scuba diving?
• I used to have goldfish but it wasn't like this.
• I've been diving before and it wasn't nearly as colorful as this.
• One reaction I find quite rewarding is when people simply stand there and say wow. (repeatedly)
• But being of Christian faith, I think my all time favorite comment was when one individual out of the blue stated "I've always believed in evolution but after seeing this I think there must be a creator."

Acknowledgements

I would once again like to thank Advanced Aquarist's for their interest in featuring my reef and as previously mentioned it's an honor. I also want to thank all the people who have helped to educate me and given their support since I got started. I would also like to thank the suppliers that have put up with my bending their ear trying to learn from their knowledge. There are so many people I have learned from, too many to mention here but I again want to thank all those who have willingly shared their knowledge, time and friendship. Thanks also to Mike Paletta who was very gracious in giving his blessing when I asked to borrow his idea. I especially want to thank my wife Penny for her years of unquestioning support and always giving me plenty of room to run with my dreams.

Summary

My aquarium's look and especially my tastes have continuously evolved. This amazing hobby has taken me up and down and back and forth, through euphoric feelings of reward to great depths of frustration. It is said that experience is what you get when you were doing one thing and expected something else. All the "school of hard knocks" experiences along with my desire to learn and improve have brought me to where I am today and I wouldn't trade them for anything else. There are of course many things I would do differently if I had a "do-over" but overcoming challenges and hard lessons are often the best teachers. I still have much to learn and am never satisfied for very long with what I've achieved so more changes to my reef are imminent. But for now anyway, I have what I would call an "SPS dominated Mixed Reef." With my reef continually growing and corals so often crowding each other, I have found that regular pruning is necessary so starting a "frag business" became the next logical progression of the hobby for me. Having frags available creates an opportunity for me to meet lots of great people in the hobby, make a lot of cool trades and even get a few costs covered now and then. This hobby has had quite a profound effect on me and has even changed the way I scuba dive. I used to mainly look for the big things; dolphins, rays, turtles, sharks, eels, etc which I will always enjoy seeing, but since having my own reef I spend more of my dives looking at coral details and the small things many people miss such as Christmas tree worms, nudibranchs, flatworms, tunicates, etc. I enjoy it more than ever. I hope that my write up and pictures have provided a little something for everyone to enjoy and that my love for the hobby is apparent through my story. I wish you all good luck and happy reefing.

With full realization that I'll get email stating that 'clams are not corals', I can not be content to leave it at that. So, I will make an even bolder statement - Tridacna clams' tissues (along with certain other genera) are colorless and contain no spectacular pigments. You are paying good money for an optical illusion. But what an illusion!

This month, we will continue our observations of marine invertebrate coloration with a slightly different subject - that of the impressive appearance of photosynthetic clams (mostly Tridacna and Hippopus species, but also including Fragum, and Corculum specimens). Strangely enough, and contrary to information in many hobbyist references, these clams do not contain colorful pigments. The 'metallic' iridescent colors we often see are caused by light reflected from tiny internal structures. Also involved are refraction, light interference and possibly diffraction. To understand why these colors are apparent necessitates a review of a few optical physics terms.

Definitions and Examples

Coral coloration (due to reflection and fluorescence) is relatively simple when compared to the science involved with clam coloration. Take a deep breath, and we'll get started.

Diffraction: Bending of light waves around an object. The colorful surfaces of CDs and DVDs are good examples of diffraction.

Hue: One of three attributes of color (along with chroma and lightness). This attribute is described with names such as 'red', 'yellow', etc.

Interference: A characteristic of light waves under certain circumstances to reinforce or cancel hue. Reinforcement is called 'constructive' interference while cancellation is called 'destructive' interference. Interference is caused by light waves traveling at different speeds and staying in or out of phase. If the light beams are of the same orientation after reflection/refraction, no color will be apparent. However, certain colors will be amplified if beams are out of phase (within a very small range).

An example of interference can be seen when two pebbles are dropped into a tub of water. Some waves will combine and become larger while others' energies meet and 'cancel out.' Basically, the same thing can happen with light waves during constructive or destructive interference.

The colors of soap bubbles or oil on water (and Tridacna iridescence) are due to constructive and destructive interference (See Figure 1).

For a tutorial on interference, see:

http://www.glenbrook.k12.il.us/gbssci/phys/class/waves/u10l3c.html

Iridophore: For our purposes, iridophores are the iridescent patches of color scattered across the mantle of Tridacna clams. An iridophore consists of numerous smaller bodies or cells called iridocytes. In turn, iridocytes contain uniform, regularly spaced stacks ('laminate' iridosomes) of sulfur-rich protein called iridosomal platelets. See Figure 2.

Iridophores and their various substructures have been described in T. maxima (Fankboner, 1971; Farmer et al., 2001; Kawaguti, 1966); T. gigas (Griffiths et al., 1992); T. crocea (Griffiths et al., 1992); T. squamosa (Fankboner, 1971); Hippopus hippopus (Griffiths et al., 1992); and T. tevoroa (Klumpp and Lucas, 1994). It is believed other photosynthetic clams contain them as well.

Note that clam iridophores are made of different proteins than many other animals' iridophores. For instance, cephalopod (squid, octopus, etc.) iridophores are based on a different material (guanine, which is why their iridophores are sometimes called guanophores. If that sounds a little odd - it is. Guanine was originally isolated from guano, or bird poop. This little known fact can make you the life of the next black tie cocktail party you attend…and make you wonder about the motivation of some scientists!).

Iridescence: An optical phenomenon in which hue ('color') changes with the viewing angle.

Reflection: The 'return' or 'bouncing back' of light waves, sometimes (but not always) without alteration of the light and incident angle.

Refraction: Deviation or 'bending' of light waves as they pass from one medium to another of different optical density. The amount of 'bending' caused by a material is called its refractive index.

Mirages are due to refraction caused by layers of cool and warm air.

Schemochromes or 'Structural Colors': Those colors caused by presence of tiny light-reflecting structures and optical physics such as refraction, interference and others. Schemochromes are the opposite of biochromes (which contain true colored pigments). Therefore, schemochromes are not actually pigments but only an optical illusion caused by structural properties (and widely seen in many bird feathers, reptile and fish scales and tissues, insects and marine invertebrates).

To stitch this information together - the 'metallic', iridescent colors displayed by Tridacna and other taxa are not true pigments (biochromes) - they are schemochromes. Schemochromes are due to physical structures within tissues. In the case of colorful clams, these structures are called iridophores. Iridophores contain uniform, protein-rich cells called iridosomal platelets. When light strikes the iridosomal platelets, it is reflected but not without modification. The color reflected is dependent upon the refractive index of the protein, its orientation, number of platelets in the stack, angle of illumination and other factors. Thus, light falling upon the platelets is refracted (due to different optical densities). Construction and destructive interference now come into play. Again, depending upon the refractive index and possibly the orientation of the proteins, interference can reinforce certain colors, or cancel them. These refracted/reflected light waves can be very dramatic in appearance if the background is dark.

If the exact refractive index is known (and, to my knowledge, it is not for Tridacna and others), then the apparent color can be predicted. Constructive interference (assuming a refractive index of 1.42) would occur at wavelengths in the range of ultraviolet (355nm) through blue (468nm; Griffiths et al., 1992)*. In other words, the structural colors reflect ultraviolet light (which we cannot see) and those visible wavelengths of violet and blue (which is the color of many clams' mantles). Different refractive indices could lend any number of visible colors.

* Note: These researchers believed preparation of mantle samples may have caused some shrinkage, thus throwing a small monkey wrench into the works. When the calculation is 'corrected' for this potential error, the constructive interference range is extended into the green portion of the spectrum (and, as we know, violet, blue and greens are quite visible in mantles' reflected light).

Discussion

If we have in mind a concept of what causes clam iridescence, then the next logical question is 'why?'

The most popular theory seems to be one of photoprotection, where potentially harmful ultraviolet (UV) radiation and Photosynthetically Active Radiation (PAR, especially in the violet/blue/green portions of the spectrum) are simply reflected away from the animal and its symbiotic algae.

A simple test, though certainly not conclusive, would be to compare clam coloration to depth. Theoretically, clams reflecting blue and green light would be found in shallow depths. See Table 1.

Table 1. Common clam coloration and depths. Casual observation suggests blue and green colors are common in clams from shallow water, while yellows and browns are often seen in specimens from deeper water. Is it really so?

Species	Common Depth	Common Colors
Tridacna crocea	to ~6m	Blue, Green
Tridacna maxima	Common to 7m, but to ~20m	Blue, Green, Violet
Tridacna squamosa	To 15-20m	Golden Brown
Tridacna trevoroa	20-33m	Brownish-Gray
Tridacna gigas	20m	Green-Brown
Tridacna derasa	4-10m, but to 25m	Golden Brown
Hippopus hippopus	to ~6m	Dull Greenish Brown

Before continuing, it should be noted that any attempt to associate fashion (coloration, in this case) with function is notoriously difficult. However, with that said, generally we see blue and green coloration associated with clams often found in shallow depths, with yellow-browns at deeper depths. However, there are major exceptions to this apparent trend where clams of a single species at the same depth display radically different coloration (see Fatherree, 2006 for some striking examples). Hippopus specimens also buck the trend.

So, other factors should be considered, such as genetic variability among specimens and possible effects of environmental factors. 'Types' (clades) of zooxanthellae found in photosynthetic clams should be studied when examining maximal depth ranges of clams.

Genetic Differences Between Differently Colored Tridacna gigas and Effects of Light Intensity and Quality on T. maxima

Burton (1997) used a laboratory procedure called electrophoresis in an attempt to link mantle 'coloration' and genetic variations. No clear relationship was established (although some interesting anomalies were observed in some of his colorful T. gigas specimens). This researcher believed unspecified environmental conditions (perhaps in conjunction with genetic predisposition) could cause 'expression of color'.

The most common environmental factor mentioned in hobby literature is that of light intensity or spectral quality. Alo (2005), in tests involving almost 400 T. maxima specimens distributed in 12 greenhouse systems and using different lighting setups in each system ('full greenhouse' light - peak PAR of 1,300-1,400mmol×m²×sec; 'shaded greenhouse' light - peak PAR of 700-1,000 mmol×m²×sec; and 10,000K metal halide light - maximum PAR of 1,450 mmol×m×sec, decreasing to 280 mmol×m²×sec (!) after 13 weeks), found only one T. maxima to shift coloration (from green to yellow) during the experiment's progress (this specimen was held in a 'shaded greenhouse' tank). However, during the clams' light acclimation period (an initial 5-hour photoperiod increased by 30 minutes daily until a 12-hour photoperiod was obtained) fourteen clams changed from green to gold, and two switched from blue to gold.

Of interest to many hobbyists is one of Alo's observations - those clams maintained under the 10,000K metal halide lamps never expanded their mantles as fully as those exposed to natural sunlight of any intensity. His work suggests spectral quality was in play, and he attributes statistically significant high clam mortality to the UV-A spike at 365nm in the metal halide's spectrum (which is an interesting observation, since other researchers have suggested refractive/reflective qualities produced by iridophores protect mantle tissues/zooxanthellae from UV-A radiation. Since the metal halide lamps were suspended 20 cm (8 inches) above the water surface, is it possible that infrared radiation - heat - generated by the lamps was transferred to the clams resulting in stress?). For those wondering, Alo keep careful records of nutrients within his systems.

This researcher also includes some interesting work determining reflectance of clams' mantles using an Ocean Optics spectrometer and its software (See Figures 3, 4 and 5).

And… A Final Clue

If Tridacna clams' coloration plays a part in preventing zooxanthellae from getting too much light, we would see this as lack of photoinhibition in photosynthesis (or specifically, a linear increase of electron flow as light intensity increases - this determined by a PAM fluorometer).

And this is exactly what we see (as shown in Figure 6). However, this is not proof that the mantle coloration is responsible - it could be due to self-shading of zooxanthellae within the relatively thick mantle, or some other factor.

This experiment was conducted while using an Iwasaki 400-watt 'daylight' metal halide as the illumination source. No photosaturation (much less dynamic photoinhibition) was noted at PAR values approaching 600 µmol·m²·sec, or ~30,000 lux. This does not mean the clam requires this amount of light; merely that it can tolerate it. T. maxima specimens can do just fine when maintained under much less light (200-300 µmol·m²·sec, or 10,000-15,000 lux, is generally sufficient).

Zooxanthellae Clades Found in Giant Clams

As we near the closing of our discussion, we should examine the 'types' of zooxanthellae known to infect Tridacna clams. Reasons for including this information are two-fold. First, it establishes that clams of the same species can contain different zooxanthellae 'types' (clades). It also suggests that animals in the listings could possibly have the same light requirements.

As to the real question - Is there a genetic link between a particular clam recognizing a specific symbiont clade and a need for photoprotection via optical manipulations?

A3 - Found in a Tridacna clam (species unreported, Baille et al., 2000), Tridacna crocea, T. maxima, T. derasa, T. gigas, and another 'giant clam' (Hippopus hippopus; LaJeunesse, 2001). Clade A3 is tolerant of higher light levels (Hennige et al., 2006). Known hosts include the jellyfish Cassiopeia mertensii from Hawaii (LaJeunesse, 2001; LaJeunesse et al., 2004), Montastrea faveolata (Belize, across a depth range of 2 to 8m), a Belizean stony coral (Siderastrea intersepta, @ 8-15m; Warner et al., 2006), the anemone Condylactis gigantea, stony corals Acropora palmata, shallow-water Acropora cervicornis, and Stephanocoenia michelini. A3 zooxanthellae are known to produce 1 ultraviolet-absorbing compound - the MAA mycosporine-glycine (Banaszak et al., 2006).

C1 - Found in Tridacna derasa (1-8m); T. gigas (1-8m) and T. maxima (1-8m). Clade C1 is considered a 'generalist' zooxanthellae in that it infects a large number of photosynthetic hosts in the Pacific as well as the Atlantic, and is distributed over a wide variety of depths. Thus, corals and clams containing this clade could be considered highly adaptive in that they can tolerate high light but are probably best suited for lower light intensities. Clade C1 (along with C3, C21, C3d, C1c and C45) is believed to be an ancestral type from which other clades evolved (LaJeunesse, 2004). Acropora cervicornis (Baker et al., 1997), Acropora divaricata, A. humilis, A. hyacinthus, A. longicyathus (from the GBR; van Oppen et al., 2001), Acropora palifera (from Taiwan, Chen et al., 2005), Acropora sarmentosa , A. tenuis (GBR; Van Oppen et al., 2001), Astreopora (GBR, LaJeunesse et al., 2003), Astreopora myriophthalma (Taiwan; Chen et al., 2005), Caribbean anemones Bartholomea and Condylactis spp. (LaJeunesse et al., 2003), Great Barrier Reef 'corallimorpharia' and Coscinaraea, Coscinaraea wellsi and Cycloseris vaughani from Hawaii (LaJeunesse et al., 2004), Cyphastrea (LaJeunesse et. al., 2003), Cyphastrea chalcidicum (van Oppen, 2005), Atlantic and Pacific Discosoma spp. (LaJeunesse, 2005), Echinophyllia orpheensis, Echinophyllia lamellosa (Chen, 2005), Caribbean Eunicea (LaJeunesse et. al., 2003), Euphyllia ancora, Euphyllia glabrescens (Chen, 2005), Favia (LaJeunesse et. al., 2003), Favia favus and Favites abdita from Taiwan (Chen, 2005), Fungia (LaJeunesse et. al., 2003), Fungia crassa (van Oppen, 2005), Galaxea, Goniastrea (LaJeunesse et. al., 2003), Goniastrea rectiformis (Chen, 2005), Goniopora (LaJeunesse et. al., 2003), Goniopora columba, Goniopora lobata (Chen, 2005), Herpolitha, Hydnophora (LaJeunesse et. al., 2003), Hydnophora excessa (Chen, 2005), Icilogorgia, Lebruna, Leptastrea (LaJeunesse et. al., 2003), Leptoria phrygia (Chen, 2005), Leptoseris incrustans (LaJeunesse, 2004), Linuche, Lobophytum, Merulina (LaJeunesse et. al., 2003), Merulina ampliata (Chen, 2005), Merulina scrabicula (van Oppen, 2005), Millepora sp. (LaJeunesse et. al., 2003), Montipora aequituberculata (Chen, 2005), Montipora cactus from Indonesia (van Oppen, 2004), Montipora cactus, Montipora curta from Taiwan (Chen, 2005), Montipora confusa (van Oppen, 2004), Montipora digitata, Montipora effluorescens, Montipora hispida, Montipora sp., Montipora spongodes, Montipora undata from Taiwan (Chen, 2005), Mycedium (LaJeunesse et. al., 2003), Mycedium elephantotus (Chen, 2005), Pachyseris, Paulastrea, Caribbean Palythoa, Hawaiian Palythoa (LaJeunesse et. al., 2003), Pavona desucata, Pavona frondifera, Pavona varians, Pavona venosa (Chen, 2005), the 'bubble' coral Plerogyra (LaJeunesse et. al., 2003), Plesiastrea verispora (Chen, 2005), gorgonians Plexaura and Plumigorgia (LaJeunesse et. al., 2003), Taiwanese Pocillopora damicornis (Chen, 2005), Polyphyllia, Porites sp. (LaJeunesse et. al., 2003), shallow-water Porites cylindrica, Porites lutea, Porites solida (from Taiwan; Chen, 2006), GBR Psammocora (LaJeunesse et. al., 2003), Pseudosiderastrea tayamai (Chen, 2005), Rhodactis, Rumphella, Sarcophyton, Pacific Scolymia, Siderastrea, Sinularia (LaJeunesse et. al., 2003), Stylocoeniella guentheri (Chen, 2005), Stylophora sp. ((LaJeunesse et. al., 2003), Stylophora pistillata (Chen, 2005), Turbinaria sp. (LaJeunesse et. al., 2003), Turbinaria mesenteria (Chen, 2005), Pacific and Caribbean Zoanthus spp. (LaJeunesse et. al., 2003).

Clam Coloration - Is It Camouflage?

Reflection of ultraviolet radiation could serve as a photoprotective measure to both host and symbiont, but is a poor idea for camouflage since many fishes can see well into the ultraviolet radiation range. Of course, the same applies to visible radiation. It would seem that clam mantle coloration is just the opposite of the best camouflage strategy - that of invisibility, such as offered by transparency, where background light is transmitted through tissues. Further, the apparent self-protection reaction made possible by clams' photoreceptors (primitive 'eyes') to shadows is well known - the sudden closing of the valves, where water is forced out of internal cavities (usually enough to scare away predator fishes, such as Thalassoma wrasse spp. This, naturally, does not exclude camouflage's potential of predator avoidance, if you will. However, some researchers believe mantle coloration acting as camouflage to be a remote possibility).

There is also the possibility that physical qualities of the mantle could enhance photosynthesis. However, there is very little evidence supporting this hypothesis and it will not be discussed here.

I present this information for those truly interested in pursuit of answers. Unfortunately, I can no longer work on this since NELHA donated their Tridacna clams to the Waikiki Aquarium.

It should be apparent that we have a fairly good understanding of how clams' mantles are colorful, but a very poor one of why they appear this way.

This is an excellent project for a dedicated hobbyist to undertake. Quality spectrometers are becoming increasing affordable as diffraction gratings find their way into different applications, and a fair number of instruments are now in hobbyists' hands. Those hobbyists willing to expend their time and money could be rewarded with unlocking mysteries of clam coloration - how they do it, why they do it - and perhaps turning those less-than-desirable specimens into 'killer clams'.

I will be glad to assist in any way possible. Contact me at RiddleLabs@aol.com.

MACNA! Atlanta 2008! www.masna.org

References

1. Alo, M., 2005. Survivorship, growth and pigmentation responses of the marine ornamental invertebrate Tridacna maxima to varied irradiance levels in two different culture systems. Master's Thesis, University of Florida. 79 pp.
2. Baillie, B., C. Belda-Baillie and T. Maruyama, 2000. Conspecificity and Indo-Pacific distribution of Symbiodinium genotypes (Dinophyceae) from giant clams. J. Phycol. 36:1153-1161.
3. Baker, A. and R. Rowan, 1997. Diversity of symbiotic dinoflagellates (zooxanthellae) in scleractinian corals of the Caribbean and eastern Pacific. Proc. 8th Int. Coral Reef Symp., Panama. 2: 1301-1306.
4. Brocco, S., 1977. The ultrastructure of the epidermis, dermis, iridophores, leucophores and chromatophores of Octopus dolfleini martini (Cephalopod: Octopoda) Ph.D. Thesis, University of Washington, Seattle.
5. Burton, C., undated. Mantle colouration variation and genetic diversity in Lizard Island giant clams (Tridacna gigas). 14-23.
6. Chen, C., Y-W Yang, N. Wei, W-S Tsai and L-S Fang, 2005. Symbiont diversity in scleractinian corals from tropical reefs and sub-tropical non-reef communities in Taiwan. Coral Reefs, 24(1): 11-22.
7. Fankboner, P., 1971. Intracellular digestion of symbiotic zooxanthellae by host amoebocytes in giant clams (Bivalvia: Tridacnidae), with a note on the nutritional role of the hypertrophied siphonal epidermis. Bio. Bull. 141: 222-234.
8. Farmer, M., W. Fitt and R. Trench, 2001. Morphology of the symbiosis between Corculum cardissa (Mollusca: Bivalvia) and Symbiodinium corculorum (Dinophycae). Biol. Bull., 200: 336-343.
9. Fatherree, J., 2006. Giant Clams in the Sea and the Aquarium: The Biology, Identification, and Aquarium Husbandry of Tridacnid Clams. Liquid Medium, Tampa, Fla. 227 pp.
10. Griffiths, D., H. Winsor and T. Luong-Van, 1992. Iridophores in the mantle of giant clams. Aust. J. Zool., 40: 319-326.
11. Hennige, S., D. Suggett, M. Warner and D. Smith, 2006. Photoacclimation of Symbiodinium revisited: Variation of strategies with thermal tolerance? Natural Environment Research Council, University of Essex.
12. Hirose, E., K. Iwai and T. Maruyama, 2006. Establishment of the photosymbiosis in the early ontogeny of three giant clams. Mar. Biol., 148(3).
13. Johnsen, S. and H. Sosik, 2003. Cryptic coloration and mirrored sides as camouflage strategies in near-surface pelagic habitats: Implications for foraging and predator avoidance. Limnol. Oceanogr. 48(3): 1277-1288.
14. Klumpp, D. and J. Lucas, 1994. Nutritional ecology of the giant clams Tridacna tevoroa and T. derasa from Tonga: Influence of light on filter-feeding and photosynthesis. Mar. Ecol. Prog. Ser., 107: 147-156.
15. Knop, D., 1996. Giant Clams: A Comprehensive Guide to the Identification and Care of Tridacnid Clams. Dähne Verlag, Ettlingen. 255 pp.
16. LaJeunesse, T., R. Bhagooli, M. Hidaka, L. de Vantier, T. Done, G. Schmidt, W. Fitt and O. Hoegh-Guldberg, 2004b. Closely related Symbiodinium species differ in relative dominance in coral reef host communities across environmental latitudinal and Biogeographical gradients. Mar. Ecol. Prog. Ser., 284: 147-161.
17. Yoshihisa, K., undated. Organization and development of reflecting platelets in iridophores of the giant clam Tridacna crocea Lamarck: Developmental biology.
18. Zoo. Sci., 7(1):63-72.

A selection of useful tidbits of information and tricks for the marine aquarist submitted by Advanced Aquarist's readership. Readers are encouraged to post them to our Hot Tips sticky in the Reefs.org General Reefkeeping Discussion forum or send their tips to terry@advancedaquarist.com for possible publication. Next month's Hot Tip theme will be "SPS (Small Polyped Stoney Coral) Selection and Care Tips".

Clam Selection Tips:

First off it's a great honor to be chosen for the Featured Aquarium. Who would have ever known that this hobby would have taken me to the levels that I have attained within saltwater aquariums. I've been involved with the aquarium keeping scene since I was just a kid of 14 yrs old. My mother brought my first tank home on day - a 20 gallon high. I was hooked from that point on. As for saltwater, it's been a short 3 years that I have been knee deep in reef keeping! What can I say? It's an addiction to which I have not yet seen a cure.

The tank

It all started, January 2003, when I received a call from a friend who said he was moving to New York and who asked if I would like to take over his saltwater aquarium? Free of charge. How could I say no? Two and a half years later, I have two tanks going, a 15 g and a 55 g. This article details my well populated 55g reef display.

Initially, the tank was setup in August 2003 to accommodate about 80 pounds of live rock a friend had that needed a place to be housed as he repaired his leaky tank. The tank was set up with a 4-5 inch DSB and live rock. It sat empty until January 2004 when my friend decided it was time to return his live rock. In the end, I was able to keep one rock from his collection. Since I had my first SPS given to me, a chip-sized piece of Pavona, which I had glued to the center piece, I was able to keep that one rock. Granted it was his largest piece of around 18 pounds… such a great friend. That center rock still sits in its original position with a softball sized colony of the same Pavona growing on it. After that I needed to fill the tank with live rock once again. I was very fond of the Fiji rock and the Tonga branch rock so I have the complete right side of the tank filled with about 40 pounds of Tonga and the left side with approximately 30 pounds of Fiji. As the picture indicates now, the rock work has stayed in place for 2 years now - if it works, leave it alone.

Tank Specs

• 55 Gallon AGA tank, painted back with 3 coats of light blue.
• Custom Built stand and canopy, painted gloss black.
• Nova 22g sump, half filled with live rock
• Sealife Overflow
• Sealife Skimmer, rated for a 150g
• Rio 20HP return plumbed to a SQWD device for alternating current
• Blueline wavemaker with 3-Maxi Jet 1200's and one Seio 820
• 2- 175w IceCap ballasts running 14kK Hamilton bulbs
• 1-IceCap 430 VHO ballast running 2-110w 03 Actinics
• Temp probe with internal and external readout
• Ebo Jager 150w heater
• 9 inch fan for cooling, retro all the way!
• ACP 500 Battery Backup
• Kent Marine Maxxima 4 chamber RO/DI

Tank Inhabitants

Fish

• Red Tailed scooter blenny
• Yellow tang
• Copper banded Butterfly
• Yellow Clown goby
• Maroon Clown hosting a Green Bubble Tip Anemone
• Blue "DEVIL" damsel

Invertebrates

• Cleaner shrimp
• Fire shrimp
• Crabs and snails: Emerald, scarlet red legged, blue legged and various snails
• Two Sand sifting starfish, red serpent star
• Clams, 3 maxima, 2 royal blue and one golden and 1 blue corcea

Corals

• Millie's-Red/yellow, blueberry, tri-color and yellow
• Plate coral: red plate, 2 varieties, purple rim plate, plain and one with blue polyps
• Bali Slimers: green, yellow, blue, one or two of each
• Elkhorn, blue and purple tipped
• Ricordia's: green, blue and orange
• Mushrooms: 2-X-Large green hairy, blue, red, multi color tonga
• Zooanthids: blue-green-red-lime-orange
• Button Polyps: Florida greens and large yellows
• Green tipped hammer
• Green polyp leather
• Lots of pulsating xenia! Silver and beige colors
• Multi-colored open brain
• Green plate coral
• And of course a few more that unknown to me

I monitor semi-weekly:

• PH-8.2
• Salinity-1.024
• Temp-78º-82º
• Alk-6-7
• Cal-375-425
• 10% H20 water change weekly, 5-7gallons
• 5-10 g a week for top off, pickling lime is used to saturate H20
• 25 mls B-Ionic added daily
• Magnesium and Strontium, capful weekly
• No other supplements added.
• Carbon 24/7, changed monthly

I feed the tank with a mixture that was made with about 6 frozen and 3 flakes varieties combined. I also use Vita-Chem and Phytoplankton for the corals. Tank is fed once every three days. I found with less feeding I don't get ANY undesirable algae outbreaks and the tank stays a lot healthier.

Take your time, read books, visit the web and absorb as much as you can. Don't be afraid to try something new and keep up on your husbandry. (Yes, that means water changes for those that don't do them!) I feel with this regiment you will have a successful tank for many years to come. Furthermore, this hobby requires patience and money. Visiting places like Reefs.Org, I have been able to learn and obtain great knowledge from fellow aquarists that have been helpful in responding to questions, gripes, and assisted with the background know-how of our awesome hobby.

I appreciate everyone taking the time to read about my tank setup and its inhabitants. If you have any questions or comments, positive or negative, I'd love to hear from you. Racenrich@wideopenwest.com

In early 2003 it occurred to me that my old 80 gallon (330l) freshwater tank might also do for a reef tank. When I studied the various ways and approaches of reefing, I got biased towards reducing technology in favour of an utmost "natural management" of nature.

Thus I decided not to use a skimmer and also do without any kind of conventional (mechanical) filtration. Since there were no drillings in the groundplate I also dropped a sump below the tank. Into the right corner at the backside I glued in an overflow consisting of a separate compartment from where the water is immediately transmitted back into the tank.

Among the different natural filtration systems the "Jaubert System" pleased me because of its simplicity and its advantages with respect to micro life. In July 2003 I covered one third of the ground at the backside with a 5 inch high Jaubert ground which consists of a 1 inch plenum constructed of eggcrate and covered with a common fibreglass window screen. A four-inch sandbed (grain size 3-4mm) was placed on this construction. A bent acrylic strip served as a barrier to the foreground. I used silicon glue to secure this barrier.

For the lighting I confined myself to 4x54 Watt ATI T5 bulbs with good parabolic reflectors, and this turned out - contrary to common opinion- to be enough light for good SPS growth.

In the spring of 2004 the rich life and excellent coral growth motivated me to make some improvements:

• Instead of manually adding Kh and Ca liquids into the tank every day, I installed a Grotech TEC III dosing station which now adds the solutions at set intervals (currently eight times per day).
• To enhance coral colors, I changed the light spectrum more to the blue by using two ATI blue plus and two ATI aquablue special.
• To raise the pH and oxygen at night, which could become problematic in my unskimmed system, I decided to connect a second, smaller tank (35 gallon) which is kept on a reverse illumination cycle (light at night, dark during the day). The extra tank, or refugium, consists of a frag and algae chamber on one side and a sedimentation chamber on the other.

From the beginning there was a very low concentration of nutrients (NO3=0mg/l; PO4= 0-0,024mg/l measured with Merck) due to the combined efficiency of the Jaubert System, the fair amount of corals, and the regular harvesting of (blue appearing) brown algae ( Dictyota sp.). As it seems to me, to the low concentration of nutrients is an important ingredient for the rich variety of coral colours in the tank.

Hopefully this has provided you a short insight on how my tank functions.

Equipment

• Tunze Stream 6010 with multicontroller
• Aquabee 1000 (circulation refugium)
• Tetra 150W heater
• Grotech TEC III dosing station
• Zajac Pegel Plus (automatic evaporation refill)

Lighting

• 4x54W T5 (maintank)
• 2x24W T5 (refugium)
• moonlight

Maintenaince

• Daily: dosing of trace elements (AquaConnect energy elements 1-3)
• Daily: feeding various dry and frozen food
• Every 10 days: measurements of Ca and KH (KH 6-8, Ca 400-420)
• Every 5 weeks: water exchange (about 10 gallons)
• Mg, PO4, Nitrate is measured
• Once a month: top the 2.5 gallon KH and Ca canisters (with a German variation of the "Two-part additive system" called the "Balling Methode")

Fish

• Centropyge potteri
• Istiblennius chrysospilos
• Gramma loreto
• Synchiropus splendidus
• Group Chromis viridis
• 2 Gobiodon histrio
• 2 Amphiprion ocellaris
• 2 Nemateleotris magnifica
• 2 Signigobius biocellatus
• 2 Chrysiptera parasema

Invertebrates

• 2 Lysmata amboinensis
• 2 Lysmata wurdemanni
• 1 Neopetrolisthes maculatus
• 1 Stenorhynchus seticornis
• 1 blue Crocea clam
• red Bubble-Tip Anemone
• small hermit crabs (Calcinus latens, Clibanarius tricolour)
• different snails, brittlestars, starfishs,…
• some big sponges from the caribic

Corals

• About 60 different species
• Acropora
• Montipora
• Pocillopora
• Seriatopora
• Anacropora
• Porites
• Caulastrea
• Tubastrea
• Platygyra
• Euphyllia
• Blastomussa

Philosophy

• Jaubert System
• Strong water circulation
• Fishes should be kept in pairs
• Kinds and swimming behaviour of fishes should fit to tank size
• Occasional (e.g. every 6 months) major water changes (30-40%)
• Good trace elements
• Sediments should be siphoned out and algae be harvested

This article will feature a glimpse into some of the gadgets used in the marine aquarium hobby. The author frequently receives emails asking for input on products, however this article is intended to introduce readers to the vast world of aquarium products. Several of the items mentioned here have not been used by the author and should not be viewed as endorsements.

It's that time of year again. One of my favorite times of the year is when reef people around the world celebrate a Holiday Season. For me, this means the pleasure of attending another Reef Geek Holiday Party. These events are typically designed for a bunch of "Fish Geeks" to get together and enjoy the company of other overly obsessed hobbyists. Another enjoyable part of these events are seeing new aquarium products, with freebies and donations as well.

For some of you in large hobbyist clubs and public aquaria the fun and games of Reef Parties is all too familiar. For everyone else, here is a look into what you may be seeing in stores this Holiday Season.

Low Budget Items

Can you believe all the little things you can buy in this hobby? I believe it to be only second to the scuba diving hobby. From digital thermometers to hand held magnifying glasses to fish foods to hermit crabs, low budget items are everywhere. Some hobbyists have even been known to make Christmas Stockings that are stuffed with all aquarium related items.

Middle Budget Items

Well these are the gifts for that special friend you might have. Say someone like your local aquarium club president! If that doesn't work, you may want to consider treating yourself this holiday season with one of these additions to your aquarium.

High Budget Items-

High budget items are not usually the best gifts to give, but are certainly the best gifts to receive. Honestly purchasing a High Budget Item is often unnecessary as most of these items are chosen by hobbyists for specific purposes. I would like to review some of these products because some of you may be fortunate enough to convince a significant other that you really need one of these items. If that is the case, I certainly recommend that you pick out the exact style and manufacture that you are looking for.

To see the Wave2K in action click on this link for the above tank video, and the in tank video.

The Important Part

Let us not forget the important things during the Holidays. The best part of a Reef Geek Party is the camaraderie and enjoyment of seeing friends. I hope all of you will enjoy the Holidays with your fishy friends as much as I know I will.

Author Information

Adam Blundell M.S. works in Marine Ecology, and in Pathology for the University of Utah. He is also Director of The Aquatic & Terrestrial Research Team, a group which utilizes research projects to bring together hobbyists and scientists. His vision is to see this type of collaboration lead to further advancements in aquarium husbandry. While not in the lab he is the president of one of the Nation's largest hobbyist clubs, the Wasatch Marine Aquarium Society (www.utahreefs.com). Adam has earned a BS in Marine Biology and an MS in the Natural Resource and Health fields. Adam can be found at adamblundell@hotmail.com.

Introduction

I would first and foremost like to thank Advanced Aquarist for selecting my reef tank as a Featured Aquarium.

I have always had a fascination with marine life, its beautiful colors, diversity, unusual life forms and its delicate balance. When ever I was around aquariums I could just stare at them for hours. In March of 2003 decided that it was time to get into the hobby of reef keeping. After reading a few books and websites on the subject of reef tanks and consulting with the LFS employees, I ended up getting the biggest tank I could realistically fit into my room. The tank is the very same that you are looking at right now.

General Information

When I decided to get 72 gallon bow front AGA tank, I needed to figure out what kind of filtration I would need. However being new to the hobby I was overwhelmed by all the equipment that was needed. That's when an LFS owner introduced me to the "Miracle Mud" system. This sounded like a great idea to me because all the filtration would be done biologically, and I would not need a skimmer or any kind of supplementation reactor. I also thought it would be important to set up as natural reef environment as I could, the kind that would rely on itself rather then equipment. In the three years since the initial setup the system is almost exactly the same, with just a few minor adjustments here and there. The only problem with this system is that it would take a lot longer for it to establish itself. I didn't add lights for the first 3 months or add any corals for the first 4 months, and didn't start adding fish for 6 months. However after that things looked great and the tank grew and flourished into what you see today.

Aquascaping

My goal was to recreate a natural reef, with the over all appearance of the tank being more important then any particular fish or coral. I used about 120 lbs of live rock to create the kind of look I liked. Since then I have not moved the rocks at all, because I knew with time it will start look natural as long as I would just leave it alone. For substrate I mixed sand with crushed coral to create 1" deep shallow sand bed. All of the corals were purchased as small colonies or frags. In my opinion if you would like your tank to look natural, you must get corals small and let them naturally grow where they please. With that said I usually don't move any of my corals unless absolutely necessary.

Aquarium Profile

• 72 gallon All Glass Aquarium and stand
• 20 gallon custom Miracle Mud refugium
• DIY canopy
• Dimensions 48" x 18" x 23"

Lighting

Lighting consists lighting is two 250watt 10K Coral Vue metal halides, and four 65 watt PC actinics. The schedule is as follows: 10am two of the PC's turn on, 10:30am the other two turn on. At 1pm the metal halides turn on and stay on for 6 hours per day until 7pm, PC's stay running for 12 hours (10pm and 10:30pm). All the lights are on digital timers to make sure the lighting schedule is precise. The metal halides and power compacts are on magnetic ballasts. Two 4.5" cooling fans are on the entire time the lights are.

Filtration, Circulation & Chiller

Most of the filtration is biological; it consists of a 20 gallon refugium with a 3" deep miracle mud sand bed and Caulerpa macro algae. Lighting the refugium is a 25watt florescent light that stays on 24 hours a day, in order to make sure that Caulerpa does not go into sexual production. The display also holds about 120lbs of live rock that helps with breaking down waste. For chemical filtration I run two small bags of carbon, I also put a small bag of Phosban in a few of months ago. The only mechanical filtration is a 100 micron sock filter.

The whole system is driven by a MagDrive 12 (1200 GPH) submerged return pump, which sits inside the refugium. Drawing the water from the refugium, the pump passes it through a 1/10 HP Arctica Chiller before returning it to the tank. The chiller along with the cooling fans keeps the tank at 80 º-82 ºin the summer and at 78 º-80 ºin the winter. For maximum ventilation the chiller and the light ballasts are located outside of the cabinet.

In addition to the Mag 12 return pump, two Seio 820 GPH power heads provide the water movement inside the tank. The power heads are positioned with the intent to provide more flow to the SPS side of the tank, and less to the LSP side.

Calcium & Alkalinity Supplementation:

As I have stated earlier I do not have any kind of a calcium or kalkwasser reactor. In order to keep up with the uptake of calcium, a 2.5 gallon kalkwasser top off drip is set up.

Having no rector, I have to make sure that the salt used to make water changes has high levels of calcium, alkalinity and magnesium. I am currently using Oceanic salt and have been happy with it for the most part.

Water Parameters:

• Calcium: ~ 420 PPM
• Alkalinity: ~ 6-7 dKH
• Specific Gravity: ~1.025
• pH: ~ 8.2
• Temperature: 80.0º - 82.0º
• Nitrate: Undetectable
• Nitrite: Undetectable
• Phosphate: Undetectable

Feeding

I used to feed three times a day which included an entire cube of frozen food and flake food. After a while I figured I should cut back a little, so I started feeding the fish once a day with a quarter cube of Special Formula VHP frozen food, and a quarter cube of Formula One frozen food. Every 3 days or so I feed the fish Formula Two flake food instead of the frozen food. Usually I feed the fish at about 8pm after the metal halides turn off (I feed in small quantities to make sure all the food is eaten, it takes 3-4 times to feed all the food). I tried feeding phytoplankton, but stopped because I didn't notice any difference in my livestock.

Livestock

Fish

I carefully selected the most colorful and beneficial fish for my reef. It was very important that all the fish are reef safe, and not aggressive towards each other.

• Purple Firefish (Nemateleotris decora) 20
• Possum Wrasse (Wetmorella nigropinnat) 25
• Six Line Wrasse (Pseudocheilinus hexataenia) 20
• Flame Wrasse (Cirrhilabrus jordani) 70
• Red Sea Purple Tang (Zebrasoma xanthurum) 60
• Coral Beauty Angel (Centropyge bispinosus) 25
• Pair of Bartlett's Anthias (Pseudanthias bartlettorum) 60

Invertebrates

Clams

The clams are the main source of exotic color in the display and have been with me for almost two years. In that time the Derasa clam (located in the left hand corner) has more then tripled in size to become about 10", and is running out room in this tank. The Maxima and the Crocea have also shown a substantial amount of growth.

• Derasa Clam (Tridacna derasa) 110
• Super Color Crocea Clam (Tridacna crocea )
• Super Colored Maxima Clam (Tridacna maxima) 150

Other Invertebrates

• Feather Duster (Sabellastarte sp.)
• Blue Tuxedo Urchin (Mespilia globulus) 20
• Mated Pair of Scarlet Skunk Cleaner Shrimp (Lysmata amboinensis) 20
• Various Hermit crabs
• Various snails

Corals

I like to keep a mix of different hard corals, because I like the display they create together. The LPS corals have gotten very big over the last couple of years, as I almost don't frag them unless they are killing each other. Some of the SPS have also shown tremendous growth, most notably the Purple rim Montipora Cap that occupies most of the bottom right corner of the tank, and is fragged rather frequently. I also have various types of mushrooms which really fill up the spaces between the hard corals. The mushrooms are however rather pesky, due to the fact that they grow out of control and have done some serious damage to some of the SPS colonies in the past.

LPS

• Candy Cane Coral (Caulastrea furcata)
• Trumpet Coral (Caulastrea curvata)
• Euphyllia Torch Coral (Euphyllia glabrescens)
• Cynarina Button Coral (Cynarina lacrymalis)
• Frogspawn Coral (Euphyllia paradivisa)
• Cup Coral, Pagoda (Turbinaria peltata)
• Doughnut Coral (Cynarina deshayesiana)
• Favites Corals (Favites spp.)

Mushrooms

• Hairy Mushrooms (Rhodactis indosinensis)
• ActinodiscusMushrooms (Actinodiscus sp.)
• Purple Mushrooms (Actinodiscus sp.)

SPS

All of my SPS coral colonies were started as very small frags that I either traded or bought from fellow hobbyists. Rich (Jackson6745) also helped us out a lot with the SPS corals, so a big thanks to him!

• Various Acropora Corals
• Various Branched Montipora Corals
• Various Leaf Plate Montipora Corals
• Birdsnest Coral (Seriatopora hystrix)
• Pavona Coral (Pavona decussatus)
• Hydnophora Horn Coral (Hydnophora sp.)
• Pocilliopora (Pocilliopora sp. )

Maintenance

Weekly, I do a 5 gallon water change with Oceanic salt. Once a week I take out my 100 micron sock filter to clean it by putting it into the washing machine. I also clean the glass about once a week. Once a month I take out my pumps and soak them in vinegar for an hour and scrub the insides to clean out any calcium buildup that may have occurred. I also make kalk water once a week to use as top off.

Concluding Remarks

This little window into the ocean that I have created was not done over night. It took a lot of time, dedication, patience and research by both me and my brother Don; to get the tank to what is it today. Since I have started this wonderful hobby I have learned a great deal of knowledge about marine biology, chemistry, as well as reef life in general. I would like to share what I have learned so far, to help others as many have helped me. Finally to my fellow reef keepers I would like to say: do your research and have patience, those two things have been the key to my success and will hopeful help you as well.

Seashells are certainly diverse and widespread. They are loved and enjoyed by many, and have been for thousands of years. People around the world love collecting, cleaning, and displaying these ocean treasures.

This article is intended to bring attention to something treasured by many; seashells.

Background

Seashells liter the shores of beaches around the world. They serve as jewelry, currency, mementos, toys, decorations, cook ware, and an abundance of other ways. In fact shells "have stimulated the artistic, promoted ideas in design and architecture, inspired musicians and poets, and have led to the publication of some of the most beautiful books ever produced for natural historians" (Oceana 2004). Seashells are made by marine invertebrates. These invertebrates are typically in the phylum Mollusca. There are seven extant (living) and in regards to the molluscs about 3/4 of the species are contained in the class Gastropoda (gastropods). With over 25,000 species of snails (gastropods) and 10,000 species of bivalves (bivalvia) alone, the phylum can most certainly be considered speciose (Oceana 2004). Although other publications list gastropods having greater diversity, near 2/3 of the phylum at approximately 50,000 living species (Calfo & Fenner 2003).

So what are seashells? Well they are obviously the skeletal remains of molluscs. These skeletal structures serve as protective barriers for the animal's soft fleshy body. They are used for catching food, holding onto substrate, movement, body shape, and protection. How did they come about? We don't know.

The Debate

Two main theories exist on the origin of seashells. Some scientists like Sean Brennan of the US Geological Survey postulate that incredibly high ocean calcium levels may have favored organisms that could excrete calcium as a waste particle. Of course, this waste particle being shell. This theory is supported by geologist Tim Lowenstein of State University New York. Lowenstein and colleagues have used x-rays to analyze water pockets that are millions of years old. This group has speculated that their findings of high calcium levels about 540 million years ago may have been responsible for the "Cambrian Explosion" of shelled organisms.

The second popular theory of shell origin is of course for defense mechanisms. This theory is supported by Steven Stanley of Johns Hopkins University. Looking at molluscs of today the function of defense is undeniably existent. However the defensive needs of early shell producers is unknown. Additionally, there exist high costs involved in producing shells. If ridding calcium were the only purpose than a precipitate crystal would be excreted. The fact that animals invest energy into making and maintaining these shell structures indicates that they are receiving some sort of benefit from them.

Conclusion

While the debate continues on the origin of seashells, some things are certain. By looking at the shells and the animals which produce them we can certainly learn a lot about these wonderful creatures. Weather used as decorations, clothing, or currency, these items are continue to serve an important role in societies around the world.

Acknowledgments

This article is dedicated to my wife, Marzena Blundell. She is truly a lover of the sea and her appreciation for seashells is unmatched. Raised at sea as a pirate, she has grown into a great beachcombing conchologist and advocate for marine ecosystems. If only everyone could enjoy the oceans as much as she.

This article would not have been possible without the help and encouragement of Aric Blitch. His contributions with the paleogeographic information were vital. My sincere thank you to Aric for inspiring this project.

Additional appreciation is owed to the wonderful folks on Blundell Street, London England; their publications foster appreciation for all marine life.

Funding for this project was provided by the Aquatic & Terrestrial Research Team.

Author Information

Adam Blundell M.S. works in Marine Ecology, and in Pathology for the University of Utah. He is also Director of The Aquatic & Terrestrial Research Team, a group which utilizes research projects to bring together hobbyists and scientists. His vision is to see this type of collaboration lead to further advancements in aquarium husbandry. While not in the lab he is the president of one of the Nation's largest hobbyist clubs, the Wasatch Marine Aquarium Society (www.utahreefs.com). Adam has earned a BS in Marine Biology and an MS in the Natural Resource and Health fields. Adam can be found at adamblundell@hotmail.com.

References and Readings

1. Berger Foundation (2005), "The Birth of Venus- Spring", http://www.bergerfoundation.ch/Sandro/44venusprintemps_english.html
2. Calfo, A., Fenner, R. (2003), "Reef Invertebrates", Reading Trees & Wet Web Media Publications, USA.
3. Holland, J.S., (2004), "In Search of Shells' Origins", National Geographic, Vol 206 No 5, USA.
4. Lowenstein, T.K. (2001), "Oscillation in Phanerozoic Seawater Chemistry: evidence from fluid inclusions", Science, No 294, pg 1086-1088, USA.
5. Oceana (2004), "Shells", Quantum Publishing Ltd, 6 Blundell Street London, England.
6. Whitfield, J., (2001), "Salt Hold Samples of Ancient Seas", Nature, USA.