This species is easily recognized by its bold black vertical bars on a pale white to silvery body, giving it a “convict-like” striped appearance. It has an oval, laterally compressed body and grows to about 20–26 cm (8–10 inches) in length. Like other surgeonfishes, it possesses a sharp, scalpel-like spine on each side of the tail base, used for defence. The Convict Surgeonfish is primarily herbivorous, feeding almost exclusively on fine filamentous algae and turf algae growing on rocks and dead coral. It is often seen grazing actively during the day, either alone or in large schools that move across reef flats.