Grey by day in dense schools, red at night when it disperses to feed.
To about 50 cm, with a steep forehead, a deep body and a broad paddle-shaped tail with rounded lobes. Daytime schooling fish are grey to pink-grey with dark fin margins; a feeding or nocturnal fish is a strong red. Juveniles are found in shallow seagrass and rubble and carry a dark spot on the flank.
It forms tight stationary schools of hundreds through the day, usually on the up-current side of a coral head or slope, then breaks up after dark to take crustaceans, molluscs and fish over sand. The daytime school is a fixture at particular sites and can be relied on across years. Recorded from about 3 to 45 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.