The most numerous parrotfish on shallow reef, and the one whose two phases confuse most logs.
Terminal males reach about 40 cm and are blue-green with a paler patch on the cheek and a crescent of pink or yellow at the tail base. Initial-phase fish are dark grey-brown with a white band across the caudal peduncle carrying a black spot, and a pale belly. The two look nothing alike and both are numerous, so a site can appear to hold two abundant species.
It grazes algae and the surface film from dead coral and rock in the shallows, usually in groups, and is among the most numerous large herbivores on reef flats and upper slopes across the region. Like its relatives it sleeps in a mucus envelope. Sex change from female to terminal male brings the full change in pattern. Recorded from about 2 to 35 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.