Dark in front, orange behind, and watching from a hole in the reef.
To about 11 cm, typically dark blue-grey over the front half and orange over the rear, though the species runs through several colour forms including all-dark, all-pale and barred, and a single fish changes between them. The blunt head, high-set eyes and small tentacles above them are the constant features.
It occupies a small hole in dead coral, rock or a piling, reversing into it tail-first and watching from the entrance, and darts out to graze algae from the surrounding surface. It is one of the most-photographed small fish on these reefs because it holds still at the hole entrance and will tolerate a lens at a few centimetres once it has settled — which takes a minute or two of stillness after the first retreat. Recorded from about 2 to 25 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.