The purple tang (Zebrasoma xanthurum) was once a difficult fish to obtain, but thanks to increased collecting in the Red Sea, it is now a readily available and popular fish with saltwater aquarists. The purple tang is one of the few coral reef fish that is a deep blue to purple, and it has a bright yellow tail. It also earns its keep, in that it will eat some filamentous algae species.
Difficulty: The purple tang tends to acclimate readily to captivity. The only drawback to its care is it is very disease-prone (it is especially susceptible to Cryptocaryon and monogenetic flukes [black ich]). Like all surgeonfish, the purple tang must have plant material as a part of its diet; frozen preparations for herbivores, algae-impregnated flake foods and sheets of dried algae should be included in the diet. If the purple tang is housed in an aquarium with abundant algae growth, you will not have to feed it daily. However, in an aquarium devoid of plant material, the purple tang should be fed several times a day (this should include an algae sheet).
Physical description: The purple tang can be deep blue or purple with dark spots on the face, bright yellow pectoral fins and a yellow caudal fin. Small and medium-sized individual purple tangs also have darker vertical lines on the body. The largest purple tang measured was around 10 inches in length. However, most purple tangs max out at around 6 inches.
Range: The purple tang ranges from the Red Sea to the Arabian Sea. It tends to occur in relatively shallow water from 5 to 65 feet. The purple tang is found in a variety of social units, including singly, in pairs or occasionally in large shoals. These groups of purple tangs are most often formed in damselfish-dominated habitats. By forming groups, the purple tangs are able to overwhelm the territorial algae farmers, otherwise the damselfish can chase them off before they get a chance to feed. In the wild, the purple tang feeds on blue-green algae, red and green filamentous algae, and brown macroalgae.
Compatibility: The purple tang is one of the more belligerent members of the genus Zebrasoma. You will have to select purple tang tankmates carefully. The purple tang is most likely to quarrel with other herbivores, especially members of its own genus and family. The purple tang has also been known to respond aggressively to batfish, butterflyfish, angelfish and rabbitfish. Like other surgeonfish, the purple tang will use the spine in front of its tail to slice enemies. Because of its aggressive disposition, the purple tang should be the last fish introduced into the community aquarium, unless you are keeping it with large, equally belligerent species. Juvenile Z. xanthurum are not as great a threat to their neighbors as subadults and adults. The purple tang usually does great in a reef aquarium. Be aware that if underfed, the purple tang may start nibbling on large-polyped stony corals and soft coral polyps, such as Xenia. On rare occasions, the purple tang might also nip tridacnid clam mantles. Adding an algae sheet to the reef aquarium on a daily basis can help prevent this from occurring.
Aquarium conditions: An adult purple tang can be kept in aquariums as small as 75 gallons, but in aquariums that small, the purple tang is likely to make life miserable for its fish tankmates. The purple tang is more likely to acclimate if it has plenty of swimming room and several well-designed shelter sites. These hiding places should be big enough so that the purple tang can dash into them when frightened. Keep the water parameters of the purple tang as follows: pH of 8.1 to 8.4, specific gravity of 1.019 to 1.025 and a water temperature of 74 to 82.
Care considerations: The purple tang should always be quarantined before it is moved into the display aquarium. Hyposalinity treatment (reducing the specific gravity of the water in a hospital aquarium to 1.012 for several weeks) can be an effective treatment for Cryptocaryon. If you use copper with the purple tang for too long, it may develop head and lateral line erosion.
Breeding: The purple tang is not likely to spawn in the home aquarium.