Species group: Tangs and Surgeonfish
Other common names: Doubleband Surgeonfish; Spinecircle Tang; Lieutenant Tang
Scientific name: Acanthurus tennentii
The Lieutenant Surgeonfish is moderately easy to care for. Surgeonfish are continuous feeders and are primarily herbivorous. The Lieutenant Surgeonfish is considered a good choice for the home aquarium since they do not get as large as many others in the same genus. Juvenile Lieutenant Surgeonfish find it easy to acclimate themselves to the tank or aquarium but adults are reportedly very hard to acclimate. In the wild, the juveniles are initially quite wary and join small mixed groups because they seek protection in numbers. These groups consist of other Surgeonfish and various like-sized fish that will feed on the bottom and roam the edges of shallow reefs. The larger juveniles team up with others of their own species. Once the Lieutenant Surgeonfish is acclimated to its environment it is quite hardy, adaptable to a wide variety of foods, and can handle a wide range of water parameters.
The Lieutenant Surgeonfish is a thin-bodied, disk-shaped fish that has long continuous dorsal and anal fins and crescent tailfins. Their spine is like a scalpel on either side of the caudal peduncle. It is very sharp and is used by the fish for protection from predators as well as a way of establishing dominance with other fish. The Lieutenant Surgeonfish has very small ctenoid scales and a small terminal mouth with a single row of close-set teeth. The coloration of the Lieutenant Surgeonfish changes from the juvenile phase to adulthood. It is also known as Spinecircle Tang because of the vibrant coloration on its caudal peduncle surrounding the spine. Another name, Doubleband Surgeonfish, is derived from the black mark just above the pectoral fin of the juvenile which later develops into two short dark stripes in the adult Lieutenant Surgeonfish. They have a whitish grey color all over the body with darker bands behind the gills and right before the tail fin. The spine on the caudal peduncle is surrounded in black and trimmed in bright blue. The adult Lieutenant Surgeonfish found in the Maldives has a tan color with darker accent lines outlining the body. The spine is circled in a bright blue and that blue also outlines the anal fin. All varieties of the Lieutenant Surgeonfish have a forked tail fin that grows streamers as the fish ages. The juvenile Lieutenant Surgeonfish has a yellowish-gold color as opposed to the tan or whitish-grey color found in adults. Their caudal fins, too, are yellow, the eyes are black and the dark marking above the base of the pectoral fin is crescent shaped.
They can be kept with a variety of tankmates but they will be aggressive towards other Tangs, Surgeonfish, and fish with similar body shapes and color. They can be territorial, especially with new additions to their aquarium. These Surgeonfish can handle themselves well with more aggressive fish like Triggers, large Wrasses, and Puffers.
The Lieutenant Surgeonfish can be housed in a 100-125-gallon or larger aquarium. These Surgeonfish are quick, agile swimmers and need plenty of swimming room. They also require plenty of rocks and corals to hide in and to wedge themselves into at night for sleeping.They like a lot of water turbulence as opposed to a placid aquarium. They thrive with good water movement because they need a lot of oxygen, and they enjoy water rushing over their gills at times. They do not harm corals or invertebrates. However, they are voracious algae eaters and are therefore useful in a reef environment. Normal lighting conditions are acceptable since the Lieutenant Surgeonfish is found in sunlit areas. If bright lighting is used, some areas must be kept dim. Surgeonfish are susceptible to bacteria resulting from organic buildup, which deteriorates water quality. Vigorous filtration, protein skimming, and regular small water changes are, therefore, very essential.