The sailfin tang (Zebrasoma velifer) is a marine reef tang in the fish family Acanthuridae. They may live at water depths of 1 - 60 m (3 - 200 ft) or more. The fish grow to a maximum length of 40 cm (15.8 in). It has an extensive range throughout Oceania, the Indian Ocean, and the South Pacific. Zebrasoma velifer is a popular fish in the aquarium trade. They are herbivorous fish specializing in filamentous algae. Though their skin is light beige with stripes, it can turn dark brown under stress. This species is one of the largest members of its genus. The largest scientifically measured sailfin tang was 40.0 cm (15.7 in). The body of the sailfin tang is disc-shaped with a much elevated dorsal fin and a big anal fin. It has an extended snout. Compared to the other members of the genus Zebrasoma, the sailfin tang has larger but fewer pharyngeal teeth. On each side of the caudal peduncle is a single sharp spine (the so-called scalpel) which is used for defence and to establish dominance. When the fish is not using its scalpel, it is folded down inside a groove. (Source: Wikipedia.org, CC BY-SA)