Husbandry: Invertebrate Selection and Companionability
The Brittle Star literally and figuratively intertwined in a healthy reef ecosystem. Photo by Richard Ling (Creative Commons)
The proper selection of invertebrates is critical to achieving a balanced marine ecosystem, and this week the subject of husbandry within your aquarium will focus on invertebrates and how their presence can also help improve the health of your aquarium. There are plenty of aesthetically pleasing crabs, shrimp, snails, and starfish to be found on the market; As with the relationship between fish and coral, the aim is to find invertebrates that are compatible with the existing specimens in the aquarium.
Most of the hermit crabs, snails and shrimp sold at your local fish store will typically be referred to as the “clean-up crew”. This term infers a collection of animals that clean your aquarium of dissolved or decaying organics and detritus. "Clean-up crew" critters are mostly foragers and scavengers, leaving the hard work of predation to larger, more formidable organisms. They are very effective "utilitarian" animals and make great additions to your reef.
An algae outbreak is one the worst nightmares for hobbyists due to its negative impact on the aesthetic quality and health of your tank. Most snails are purchased for the control of nuisance algae and the consumption of decaying organic matter. Common algae-eating snails include Trochus, Turbo, Margarita, Abalones, and Astrea. The addition of snails such as Nassarius, Nerites, Cerith, and Conches can help control detritus in your reef.
Blue Legged Hermit Crab (Clibanarius tricolor). Photo and Hermit Crab article by Richard Aspinall
Crabs are a benefit to your tank for the same purposes as snails. Hermit crabs, in particular, are arguably better buys than most snails as they are more active and effective at both algae consumption as well as scavenging. An inexpensive and readily available member of the clean-up-crew, most hermit crabs are communal creatures exhibiting a curious and social nature. There are many species of hermit crabs, some of which are not "reef safe" so take caution when selecting hermit crabs for your marine aquarium. Blue Legged Hermit Crabs (Clibanarius tricolor) and Scarlet Reef Hermit Crab (Paguristes cadenati) are the two most popular "reef safe" hermit crabs and are both very lively additions to the tank.
There are a great variety of other crabs available to hobbyists. Like hermit crabs, some crabs are great additions, while others are not "reef safe." Some crabs also have very special requirements, so research carefully Here are two good articles to help you make your selection:
Shrimps (decapod crustaceans)
are also popular additions to reef tanks, and for good reason. Known for the distinct red and white stripes running down its back, the most commonly kept shrimp in the hobby is the Cleaner Shrimp (Lysmata amboinensis). A shy but inquisitive creature, the Cleaner Shrimp will learn to take pieces of food right from your hand. Its natural tendency to remove parasites and other harmful organisms from fish is one of the most notable and beneficial forms of symbiosis found in the hobby today.
Another type of shrimp is commonly called the “Peppermint Shrimp” (Lysmata wurdemanni complex and L.boggessi). This ornamental crustacean is distinctly colored with red bands running all over its body and has an almost opaque exoskeleton. They are excellent scavengers natural and their natural ability to consume and control a nuisance form of anemone called Aiptasia sp. qualifies the peppermint shrimp as a great addition to any mixed reef aquarium.
Starfish (sometimes referred to as sea stars) can add some aesthetic qualities as well as some very effective forms of cleanup. Most starfish are passive predators, feeding on sessile prey such as mollusks, barnacles and other slow-moving invertebrates. These interesting critters are readily available in the marine aquarium hobby for their association with the clean-up-crew philosophy we discussed earlier. The Brittle Starfish is among the most interestingly looking echinoderms in the world and is in a phylum with over 7000 living species offering a wide variety of shapes and coloration. Fitting just outside the direct definition of starfish, brittle stars have a centralized demarcated body that is clearly separated from their arms. This differentiation and natural flexibility lends them the ability to squeeze into tiny crevices within the rockwork making them very effective foragers. Instead of moving slowly on tube like feet like a true starfish, the Ophiuroidae group of echinoderms can scurry quickly with the movement of these agile arms. Many but not all species of starfish are very effective scavengers capable of excreting their stomach filaments through their mouth to digest their food outside of the body. In extreme cases some species can exhibit higher levels of predation and even can catch slower moving prey.
One of the most notorious starfish that is receiving a lot of media coverage right now is the aptly named Crown-of-Thorns Starfish (Acanthaster planci). This echinoderm specializes in consuming all types of coral and may inflict considerable damage to large portions of the coral reef. It is rarely if ever available in the trade but the very nature of this species lends credence to the range of behaviors and diets of many marine dwellers.
Craig Bagby's beautiful Tridacna clam nestled in corals.
Clams also make great additions to a well-established and well-maintained reef ecosystem. Tridacnids are the most commonly kept species of clams in the reef aquarium hobby, and the diffraction of light across their tissues is absolutely amazing. Containing eight species including Tridacna maxima, T.crocea, T.squamosa, and T.derasa, this family of gastropod includes some of the largest clams in the ocean, with the Tridacna gigas clam reaching up to three feet in length. Clams are a great addition to nutrient rich tanks as they are voracious filter feeders and the all thrive with the presence of symbiotic algae (zooxanthellae) that live within their mantle tissue.
Some non-photosynthetic bivalves sold at the local fish stores include Flame Scallops (Lima scabra), as well as oysters and barnacles. Because they lack zooxanthellae, non-photosynthetic bivalves rely solely on filter feeding for energy and are much more difficult to care for.
Taking the extra time to find compatibility write-ups regarding the proper selection of fish, invertebrates, and coral will vastly increase the overall health and appearance of your tank as well as significantly influence the well-being of each specimen it contains. With the definition of husbandry explained and some key terms presented, hobbyists are now better equipped to make a suitable selection of inhabitants for their marine tank. The proper method of selection will help you allocate funds more effectively by limiting the loss of fish and other animals you purchase.
Tune in next week when we discuss the common mistakes newer hobbyists often make, and see how educated purchases can save you money while making the hobby more enjoyable.