Pale blue with a black head and a yellow dorsal fin, grazing in shoals on the reef top in strong water movement.
To about 23 cm, pale blue body, black head, a bright yellow dorsal fin and a white band across the throat and lower head. The yellow dorsal separates it at a distance from the very similar Achilles tang, which has an orange teardrop instead and does not occur in the same waters.
It is an Indian Ocean fish, common in the Maldives, and it grazes algae in shoals on the reef top and the upper slope in strong water movement. The shoals are the way to see it: a single one is chased off a damselfish territory, but forty of them moving together are not, and a shoal crossing a reef flat at speed is doing exactly that. Like every surgeonfish it carries a hinged blade at the tail base, which cuts and is used against other fish rather than against divers.
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.