Aquarium Fish: Surgeonfishes, A.K.A. the Tangs
Some of the most popular fishes in the marine aquarium hobby are the surgeonfishes, all of which are in the Family Acanthuridae. Commonly known as tangs, many are very attractive, have unique personalities, and will also help keep your tank clean. However, when it comes to hardiness they're oftentimes sub-par, some can be quite aggressive, and some get too big for any but the largest home aquariums. Thus, it's important to know a little about any particular species of surgeonfish before making a decision to take one home. I'll fill you in on the group as a whole, and then give a bit of specific info about each of the species you're most likely to see offered for sale to help make things easier if you're thinking about getting one.
Surgeonfishes are a good-looking bunch for the most part, with only a few species that aren't nicely colored or at least covered with some sort of neat patterning. The pictures make that easy to see, of course, but being pretty is nothing particularly special when it comes to marine fishes. However, many surgeons stand apart from other fishes because of their personalities, which is one of the things I've always liked most about them. Like dogs that become obviously excited to see their human come home, various surgeons are often the first fishes to dart to the front pane of glass and dance around when you enter the room, even when many other fishes seem oblivious to your presence. To tell the truth, if I've ever seen a fish look genuinely happy to see me, it would have to be a surgeon. Many of them really do remind me of little aquatic dogs with their attitudes and antics.
Surgeons are also about as invertebrate-safe as a family of fishes can be. After running an aquarium maintenance business for 5 years and being in the hobby for almost twenty, I can recall only a single one of these fishes becoming a problem for corals/reef aquarium critters (see the specifics for clown tangs below). Still, there are a couple of things to bring up.
First, while working on my book about giant clams, I came across a few stories concerning surgeons and tridacnids. Apparently, an occasional surgeon will become fond of slurping mucous from the fleshy, extended mantle tissue of a giant clam. They don't actually bite the clam, but they can kill it nonetheless. The problem is that the clam will usually jerk in its mantle and pull the shell closed in reaction to being slurped on, which can wear out and stress it severely if it does it over and over. If a fish is persistent, this can actually lead to reduced heath of the clam, or even death. Still, again, I've never seen anything like this myself, and I've been keeping surgeons and clams together for the better part of two decades in my own tanks and those of past customers.
Second, Michael (2001) notes that when underfed, various tangs may begin to nip at large-polyped stony corals. I've never seen any such thing, but I feed my fishes well, so I wouldn't expect to. I recon if you're underfeeding your fishes and they start working on the corals, then that's your fault. I certainly would not consider this to be "normal" behavior for any surgeonfish.
Speaking of feeding… Surgeons love to eat, so feed them appropriate foods and feed them often. All of them are herbivores, and will eat a variety of plant and plant-based foods, but most all of them will also learn to eat other foods as well. Different species, and even individuals, do have variable diets though, and some will eat some things that others won't look at.
A diet of foods like algae-packed cubes, Spirulina or other quality marine flakes, Gracilaria, nori (sushi wrap made of seaweed), and kombu (dried kelp) is best, and they'll usually tear this stuff up and eat until they look like they'd burst if given the opportunity. Do make sure to buy unseasoned/untreated types if you get nori/kombu at the grocery though, as you don't want to add any sorts of additives, preservatives, etc. Of course, surgeons will also find some food for themselves in most tanks, as well, as they'll graze over glass and rock surfaces picking at whatever grows there. If you aren't having a very, very serious algae problem, this won't be enough to keep the healthy, though. Thus, you should feed them daily at the very least, and two or three times daily if possible. In the wild they poke around all day nibbling here and there, so as is the case with most herbivorous fishes, eating one big meal a day (or even less frequently) is not what they are used to at all.
Most will also eat lettuce, spinach, broccoli, and other greens. However, even though they'll eat these very non-marine foods, their nutritional values are questionable. This is especially so for romaine lettuce, which is very commonly used to feed them. If frozen or boiled first and then added to an aquarium it gets very soft and most tangs will gobble it up. But, they may eat it, and eat it, and eat it, and gain little, if any weight. Thus, it's probably much better to either not bother with this stuff, or to use it as part of a mixed diet. The other veggies should also only be part of a mixed-diet, as well. In addition, almost without exception, they'll become omnivorous and will eat brine shrimp, copepods, mysid shrimp, bits of chopped clam and regular shrimp, and other sorts of meaty things, too. But, the same goes here once again. These are not what a tang relies on in the wild, so they should not be the only foods given in aquariums.
I've got an odd story for you too, on the subject of feeding. Many, many years ago I had a tank that housed a yellow tang, a few damsels, a couple of clowns, and an extra-large carpet anemone (Stichodactyla haddoni). I also had a creek right next to my apartment at the time, and I used to go net up a bunch of little minnows and feed them to the anemone, which helped it grow to a relatively huge size (20+ inches). After doing this for a while, much to my surprise, the tang took a liking to the minnows, too. Seriously! I'd throw in a few tiny minnows and the tang would always chase one or two down and gobble them up. Of course, it never bothered anything else in the tank, and it lived and ate with the anemone for around 4 years. Then, it apparently strayed too close to the carpet one night and met its demise. A sad ending for one of the first marine fishes I ever owned.
Do note that I only used these freshwater fishes for feeding the anemone, and did not intend for my tang to get them. Freshwater fishes can be detrimental to the long-term health of carnivorous fishes when eaten in quantity (see Toonen 2003 for more), but the anemone loved them.
Now it's time for some bad news. As mentioned, surgeons don't tend to be particularly hardy, at least not at first. Many do not fare well during collection and shipping, but that's not all. A few can also be rather picky eaters that have a hard time staying healthy, and again, many seem to have immune systems that are sub-par. When disease strikes many are typically the first to show symptoms, and they're particularly prone to catching cases of the two most deadly maladies around, saltwater ich (Cryptocaryon) and velvet (Amyloodinium). These are both difficult to spot, especially on brightly-colored tangs, and are also difficult to treat. They'll essentially always lead to a relatively quick death of infected fishes if left untreated, as well. And trust me, if either of these gets into your tank, the tangs will get it.
There are other diseases, too, but of note are fin rot and head and lateral line erosion (HLLE). Tangs are also particularly prone to come down with either or both of these. However, unlike ich and velvet, both of these are easy to see, and neither leads to a quick death. Fin rot can be treated effectively, but HLLE is still quite a mystery, with many ideas about causes and effective cures. But, these are things for you to learn about somewhere else. Just be aware that if you buy a surgeonfish, you'll need to be extra vigilant when it comes to disease prevention and treatment.
With this in mind, I strongly recommend that you give any surgeonfish a full-term quarantine in a dedicated aquarium. Running a separate quarantine tank can be a hassle and cost a few extra dollars, but it has been shown to be worth it time and time again. The same goes for other fishes and creatures too, for that matter. Always remember that the best way to keep your fishes from catching ich or velvet, etc. is to never allow these things to make it into your main aquarium in the first place.
If you make sure to choose healthy specimens at the store, acclimate them properly, quarantine them first, and maintain great water quality, these same fishes can be quite hardy though, and most all of them can adapt well to aquarium life. So, don't think that they should be avoided. The fact is, most of them make great aquarium fishes (like I already said) when things are done right, and if they make it through the first few weeks, they'll likely be with you for many years.
The next thing to cover is their tendency to not get along with each other. Surgeonfishes are safe with invertebrates and most (but not all) will get along just fine with other types of reef-safe fishes, as well. However, in general, they don't care much for other surgeons. While many live in schools in the wild, trying to keep two or three of the same species in one tank will usually lead to trouble. Still, if the tank is big enough and several tangs of similar size are added simultaneously, their schooling nature just might override their fighting spirit and they may be okay with each other.
To make matters worse, even trying to keep different species of surgeons together can be problematic, too. Oftentimes it's possible to keep two surgeons from different genera together, such as a yellow tang (Zebrasoma) and a kole tang (Ctenochaetus), but even this may not work. This is especially so if they're not added at the same time and/or are different sizes.
If you want to have more than one, my advice is to choose specimens that don't look much alike (and belong to different genera if possible), that are roughly the same size, and to add them at the same time to a tank with plenty of room. When doing so, I've been able to mix up quite a few of them without too much trouble. Still, they may chase each other at times and flap their tails around at each other, but not to the point that it affects their health/well being. This can be highly dependent on the particular species chosen, of course.
There are some surgeons that can be downright nasty even to other sorts of fishes, though. They can chase, bite, beat, stick, and basically pester other fishes literally to their death at times, and no amount of food and/or space will stop them. This kind of behavior is seen in some species more than others, but I assure you that even the most mild-mannered species may include an occasional bad-boy that decides to beat the tar out of everyone else in a tank. Sometimes this can be bad enough that you must either take the offensive surgeon out or end up with a one-fish aquarium. Or, end up adding something even bigger and meaner to give the brute a dose of its own medicine (not what I recommend, of course).
Note that this sort of behavior can obviously be brought out when mixing the wrong fishes together, but unfortunately it can also occur when you've done everything right and made careful choices when stocking. I wouldn't say over-aggression is common, but then I wouldn't say it's really rare either. So, be warned. It can happen to you (and your other fishes).
Some species are more aggressive than others on the whole and can simply be avoided if you're concerned, but the real problem is the variability seen amongst individuals of the same species. Over the years I've found that the more behaviorally-boring a particular species of fish is, the more predictable their behavior tends to be. Likewise, those species that generally have real personality also tend to have a broader range of behaviors in aquariums. So, while I may praise surgeons for having plenty of personality, this also means that they can sometimes be quite unpredictable. In other words, if I tell you that yellow tangs tend to be quite peaceful and seemingly happy fish, you might have bad enough luck to get one that's just plain boring or mean as can be. Chances are good that you won't, but you might. Frankly, this shouldn't be anything new to anyone that's been keeping fish for long, and it certainly isn't unique to surgeons. Likewise, it makes good sense that the size of the tank they're placed in and who they're kept with will also have an effect on the behavior of these. So, again, they're behavior can vary from individual to individual in different aquariums.
Okay, I've mustered some information from various sources and mixed it with personal experience to give you a bit about the species you're most likely to see for sale. There are way too many tangs to give much detail about each species though, so you should do some more in-depth homework on a particular one if you think you want it. There are two things to note before moving on, though. I've given some maximum size numbers for these tangs, which can be found in Michael (2001) or at Fishbase.org, but specimens may not get nearly this big in an aquarium. These are maximum sizes, and any given specimen won't likely reach it, even if well fed and kept in a big tank. They simply have the potential to reach such a size, although most will likely stay at two-thirds their maximum reported size, or smaller. Also, don't forget what I just said about occasional nasty attitudes. When I say a tang is generally peacefully or aggressive towards other types of fishes, that means generally - not always. You should also assume that, unless stated otherwise, none of these is very likely to get along with other individuals of the same or similar species.
With that said, it's widely agreed upon that the Pacific sailfin is one of the most peaceful tangs available, but they can also get too big for most folks. These fish can reach a maximum length of 16 inches, and I've actually seen one about that big in a tank in Japan. It was HUGE, like the size of a pizza! Again, it's highly unlikely that one you might buy will grow so large, but even if it hits a foot, it would need quite a tank to stay happy.
And that's it!
- Toonen, R. 2003. Nutritional Value of Live Foods for the Coral Reef Aquarium, Part 1. Advanced Aquarist Online Magazine: http://www.advancedaquarist.com/issues/dec2003/invert.htm
- FishBase Global Information System, undated. URL: www.fishbase.org
- Michael, S.W. 2001. Marine Fishes: 500+ Essential-to-Know Aquarium Species. T.F.H. Publications, Neptune, NJ. 447 pp.
- WetWebMedia, undated. URL: www.wetwebmedia.com