|Angelfishes are laterally compressed tropical fishes that inhabit shallow reefs. Most are brightly colored, juveniles usually having different colors and patterns from the adults. They may be confused with butterflyfishes which are also brightly colored reef fishes. The most obvious difference is the prominent spine on the angle of the preopercle (a bony plate on the gill cover) of the angelfishes which is lacking in the butterflyfishes. Angelfishes are diurnal (most active during the day) and feed on small invertebrates, such as sponges, coral polyps and copepods. Some species are solitary and mate with only one partner for life. Others form harems where one male dominates several females. All are "protogynous hermaphrodites" which means when the male dies, the top ranked female replaces him by changing into a male.