Looking for a lively, colorful fish that likes to swim a lot? Getting a surgeonfish (also commonly known as a tang) or two may be your answer. These fish are relatively easy to feed and keep healthy; and because they do not bother coral as some tropical fish do, they are among the most popular to keep in a reef tank. Oval-shaped and very thin, with a steep-sloped forehead, they can be quite colorful with rich hues of blues, yellows, and greens. In some, the colors change as they mature.
Surgeonfish are in the Acanthuridae family. These creatures get their medical name from the scalpel-like, razor-sharp spines found on each side of the body at the base of the tail (an area called the "caudal peduncle"). The fish uses these spines as weapons when threatened, thrashing its tail around with the spines sticking out. When the threat is over, the scalpels fold forward against the body.
These fish are found in all tropical oceans, although very few species are found in the Atlantic. Most species live around coral reefs and reef patches in the Indo-Pacific and the Red Sea, where they are known for their particularly colorful varieties. Some species school in the open ocean.
Because these fish tend to swim a lot, they need a lot of open tank space. They tend to behave somewhat nervously and will dart and zip about in the tank and can easily injure themselves on corals and live rock if they don't have enough maneuvering room. Even a tiny laceration can lead to bacterial infections and parasite attacks for the surgeon and can also start an epidemic in your tank. If you have a reef tank, you must make sure that there is enough water above the coral rocks for them to take up perches.
These fish are also quite territorial, regardless of species, and will dominate the whole tank if they can, which makes space an absolute must. They are aggressive when they are first introduced and may even start some fights with tank-mates. Some tangs and surgeonfish really should not be kept with their own kind unless you have a lot of space for them to pick their territory. When you introduce this fish to your tank, be sure to move some of the corals and live rock around so that territories can be established by all.
Most aquarists will tell you it's best to keep only one of these species, but since they are so easy to keep, most reef keepers want to have more. If you decide to get two or more tangs, introduce them to your tank together to reduce the chances of conflict. Keep in mind that most of these species can grow to be quite large, reaching six or seven inches.
These fish require conditions relatively standard for a reef tank: a pH of around 8.3 (or higher, with the upper limit usually at about 9), temperatures in the upper 70s to low 80s, good lighting and aeration and a SG of about 1.024.
Almost all surgeonfish are herbivores, although some will eat brine shrimp and accept flake food. They must have algae or other vegetable matter available to them, however, or they will not survive. If you don't have a regular supply of algae to give them, you can feed them finely chopped lettuce or spinach. Although they will eat raw vegetable matter, blanching the lettuce (and using the "softer" leaves found among the inner layers of the head) will make it easier for them to digest and gain necessary nutrients.
Species for the Aquarium
Yellow Tang. Zebrasoma flavescens is an Indo-Pacific variety. It does very well in captivity providing it gets an ample supply of algae.
Blue Tang. Acanthurus coeruleus is a common fish in Atlantic coral reefs. Young fish are yellow, changing to a bluish-purple then blue as they mature.
Japanese Tang. Naso literatus is also known as the smooth-headed unicornfish. It comes from the Indo-Pacific and has striking colorful patterns, with bright orange lips and two bright orange spots on the tail. The body ranges from brownish-gray to gray. It is one of the more peaceful tangs and requires a protein source with its usual green diet. It is a relatively hardy species.
More experienced reef-keepers may want to get a powder-blue surgeonfish/tang, Acanthurus leucosternon. It is among the most beautifully colored of the tangs, with a bright yellow dorsal fin, black face and blue-hued body. This is a difficult species to care for, however, requiring impeccable water quality and a diet with a lot of algae. It is extremely aggressive toward other fish, especially those of its own kind, which also makes space a limiting factor to keeping one.