Acanthurus leucosternon

The blue surgeonfish, also called the powder blue tang or powder-blue surgeonfish, Acanthurus leucosternon, is a marine ray-finned fish of the surgeonfish family Acanthuridae, found in tropical waters of the Indian Ocean. It was first formally described in 1833 by the English naturalist Edward Turner Bennett, with Sri Lanka given as the type locality, and its species name joins the Greek words for white and breast in reference to its white chest. Adults reach an average length of about 23 centimetres and have a laterally compressed, oval body with a blue body, yellow dorsal fin, black head and white mouth, throat, anal and pelvic fins, together with the scalpel-like spine at the base of the tail that gives the family its name. It lives on shallow, clear coastal reefs, preferring flat reef tops and seaward slopes, and feeds mainly on benthic algae. Solitary, territorial and aggressive toward other surgeonfish, it is rarely harvested except for the marine aquarium trade.