Deep purple-blue with a bright yellow tail. A Red Sea and Arabian endemic and one of the most striking fish there.
Commonly around 20 cm; FishBase records a maximum of 36.7 cm, which is well above what divers see. Deep, disc-shaped and compressed, with tall dorsal and anal fins. The body is a deep uniform royal purple to purple-blue, often with fine darker speckling on the head, and the tail is bright yellow and sharply separated from it. The pectoral fins are often yellow or yellow-tipped. The mouth is small and set on a slightly extended snout for picking algae out of crevices.
Nothing else in the Red Sea looks like it. At a distance a juvenile sailfin tang or a striped bristletooth could be confused, and the uniform purple body with a clean yellow tail settles it.
It grazes filamentous algae on shallow coral and rock between the surface and 20 m, and it is notably aggressive towards other surgeonfish. Its range is the Red Sea to the Arabian Gulf, so it is close to a regional endemic. It carries a hinged tail blade like other surgeonfish.
Most people know it as the purple tang, which is the aquarium name for the same fish.
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.