The Orange Shoulder Tang (canthurus olivaceus) (Bloch & Schneider, 1801) is also known as: Orange Bar Surgeonfish, Orange Spot Surgeonfish, Olive Tang and the Orange-epaulette Surgeonfish and is a member of the Acanthuridae family.
The Orange Shoulder Tang is a very overlooked fish. At first glance its colors are not very bright, but closer examination of this fish shows that with the brownish-olive two tone coloration accented by the bright orange bar on its shoulder, it is actually a very beautiful fish to have in an aquarium.
Due to its eventual larger size, the Orange Shoulder Tang is most often displayed in large public aquariums as opposed to smaller hobby aquariums. The body of this fish during its juvenile stage is bright yellow, with just the slightest hint of blue edging on the anal and dorsal fins. Juveniles lack the orange spot or slash on its shoulder, which develops as it matures.
The "sword", "spur" or "scalpel" at the base of the tail of the Orange Shoulder Tang is not as large or dangerous as it is with some other Surgeonfish, such as the Naso Tang (Naso lituratus) or the the Achilles Tang (Acanthurus achilles) however they are still large enough and sharp enough to inflict a serious wound so be cautious when handling this fish. While the scalpel can inflict a serious cut, the major danger is a resulting bacterial infection, which can be very serious.
The distribution of this species extends from Hawai'i southward to central Polynesia and westward through Micronesia, Melanesia, the Philippines, and the East Indies.
Because of its size and constant roaming nature, the minimum aquarium size suggested for this fish is 135 gallons. As long as the aquarium is large enough a juvenile and an adult may be kept together. It is generally compatible with other non-aggressive tank mates, but if plans are to keep this species with other Surgeonfishes, it is recommended to add this fish first, or if of the same species, place them in the aquarium at the same time.
The maximum size of the Orange Shoulder Tang is about 14".
To date the Orange Shoulder Tang has not been successfully bred in captivity. In the wild, this fish, as with other Surgeonfish, is a "free spawner", with the female ejecting her eggs near the surface of the water and the male fertilizing the eggs as they drift to the surface. Once the fertilized eggs reach the surface they drift with the ocean current in the plankton layer of the ocean. The eggs mature, and the fry hatch out, still drifting in the current. The fry feed on the algae, larvae and other microscopic life in the plankton layer. When the plankton and the fry drift close enough to land, the fry descend to the bottom of the ocean, usually in the calmer waters outside of the surge zones on the reef and in bays and harbors.
As they grow the Orange Shoulder Tang will migrate to the highly oxygenated waters on or near the surge zones of the reef where it will live the rest of its life unless forced to move by forces such as a hurricane which makes the reef waters uninhabitable.
Being a herbivore this fish feeds on filamentous algae, diatoms, as well as detritus off sand bottom substrates in the wild. It is best kept in an aquarium with an open sand bottom and ample algae growth for grazing.
It usually does not bother corals. The Orange Shoulder Tang prefers a lot of live rock in an aquarium where it can easily hide when it feels threatened.
In an aquarium, this fish should be fed a varied diet including marine algae (dried seaweed) as well as meaty fare. Hanging dried seaweed (also called "Nori") in a veggie clip in the tank is an excellent way to feed this fish. The Orange Shoulder will take Mysis Shrimp, which is an excellent source of protein for this (and other) fish.