Almost black, with one white bar on the flank and a yellow-edged anal fin.
To about 19 cm, deep blue-black with a single vertical white to pale blue bar on the middle of the flank — the keyhole — and a yellow margin along the anal fin. It is the largest of the dwarf angelfishes here and the only dark one, so it is straightforward once the bar is seen; in poor light the fish reads as a plain black disc.
It grazes algae over rubble and coral, generally in small groups, and moves between shelters in short runs. It is common on the rubble margins of muck sites and on reef slopes alike. Like the other Centropyge it will not hold still in the open. Recorded from about 3 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.