The moorish idol, Zanclus cornutus ("Crowned Scythe"), is a small perciform marine fish, the sole representative of the family Zanclidae (from the Greek zagkios, "oblique"). A common inhabitant of tropical to subtropical reefs and lagoons, the moorish idol is notable for its wide distribution throughout the Indo-Pacific. A number of butterflyfishes (all of the genus Heniochus) closely resemble the moorish idol. It is said the moorish idol got its name from the Moors of Africa, who purportedly believe the fish to be a bringer of happiness. Moorish idols are also popular aquarium fish, but despite their popularity, they are notorious for their short aquarium lifespans and their difficult husbandry. With distinctively compressed and disk-like bodies, moorish idols stand out in contrasting bands of black, white and yellow which make them look very attractive to marine aquarium keepers. The fish have relatively small fins, except for the dorsal fin whose 6 or 7 spines are dramatically elongated to form a trailing, sickle-shaped crest called the philomantis extension. Moorish idols have small terminal mouths at the end of long, tubular snouts; many long bristle-like teeth line the mouth. The eyes are set high on the fish's deeply-keeled bodies; in adults, perceptible bumps are located above each. The anal fin may have two or three spines. Moorish idols reach a maximum length of 23 cm. The sickle-like dorsal spines actually shorten with age. Generally denizens of shallow waters, moorish idols prefer the flat reefs. The fish may be found at depths from 3 to 180 m, in both murky and clear conditions. The range of the moorish idol includes East Africa and the Ducie Islands; Hawaii, southern Japan and all of Micronesia; they are also found from the southern Gulf of California south to Peru. Sponges, tunicates and other benthic invertebrates constitute the bulk of the moorish idol's diet. This photograph is part of the Imagine Images Collection, hosted by Alamy.