Angelfish

With their bright colours and deep, laterally compressed bodies, marine angelfishes are some of the more conspicuous residents of the reef. They most closely resemble the butterflyfishes, a related family of similarly showy reef fish. Marine angelfish are distinguished from butterflyfish by the presence of strong preopercle spines (part of the gill covers) in the former. This feature also explains the family name Pomacanthidae; from the Greek πομα, poma meaning "cover" and ακάνθα, akantha meaning "thorn".

The larger species are also quite bold and seemingly fearless; they are known to approach divers. While the majority adapts easily to captive life, some are specialist feeders which are difficult to maintain. Feeding habits can be strictly defined through genus, with Genicanthus species feeding on zooplankton and Centropyge preferring filamentous algae. Other species focus on sessile benthic invertebrates; sponges, tunicates, bryozoans, and hydroids are staples. On Caribbean coral reefs, angelfishes primarily eat sponges, and have an important role in preventing the overgrowth of reef-building corals by eating faster-growing sponge species.

Common to many species is a dramatic shift in coloration associated with maturity. For example, young male ornate angelfish, Genicanthus bellus, have broad, black bands and are indistinguishable from females; as they mature, bright orange bands develop on the flanks and back. Thought to correspond to social rank, these colour shifts are not necessarily confined to males; all marine angelfish species are known to be protogynous hermaphrodites. This means that if the dominant male of a harem is removed, a female will turn into a functional male.

As pelagic spawners, marine angelfishes release many tiny buoyant eggs into the water which then become part of the plankton. The eggs float freely with the currents until hatching, with a high number falling victim to planktonic feeders.