A plain dark damselfish of very shallow rocky ground, farming an algal patch and charging divers that swim over it.
To about 13 cm, though the two standard sources give 10.5 and 15. The adult is a uniform grey-brown, oval and robust, with short blunt dorsal and anal fins. The juvenile is a different fish: a red-brown cap on the nape, blue spotted lines on the head, and a large black blue-ringed eyespot low on the dorsal fin.
The bicolor damselfish is the confusion and it is sharply two-toned where this one is uniform.
Shallow rocky shore in wave action, often in tide pools; the sources disagree badly on the depth range, one giving nought to three metres and the other nought to thirty. It grazes algae and detritus, and it is territorial and pugnacious. Whether it will actually go for a diver is not recorded.
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.