A butterflyfish that feeds in mid-water in schools, which almost none of the family do.
To about 18 cm, with a large white triangle covering most of the body — the pyramid — set against a dark brown head and a yellow back, dorsal fin and tail. The pattern is unmistakable and is visible at a distance in blue water.
Unlike almost all its relatives, which pick at the reef in pairs, it forms aggregations of dozens to hundreds that feed on zooplankton well off the wall, sometimes ten metres or more out. It is a species of steep outer reef and current, and is scarce or absent on the sheltered slopes that characterise the muck destinations. Photographs are made in blue water against the school rather than against the reef. Recorded from about 5 to 50 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.