Most of the fish living in the ocean are carnivores, meaning they eat some other animal. But the fish living in coral reefs have evolved many specialized feeding adaptations to enable them to take advantage of a number of food sources in addition to animals. On coral reefs as many as a quarter of the reef fish species are herbivores (vegetarians), feeding on algae and marine plants. These species have adaptations that range from the incisor-like teeth of some damselfishes to the long digestive tracts of parrotfish. Other fish species specialize in feeding on the tiny organisms that float in the water as part of the plankton. Some of these "planktivorous" fish have specialized mouths that can protrude out and scoop up plankton, and sharp, binocular vision to locate tiny food items in the water.

Even the carnivorous fish have a diversity of feeding habits and a wide range of adaptations in mouths, body shape and digestive structures that allow fish to better capture and eat different animals. There are coral polyp specialists with special brush-like teeth to help extract the coral animal's flesh from the stony case surrounding it. Invertebrate specialists feed on tunicates, sponges, sea urchins, crustaceans and worms. Coral reef fish feeding on other fish show a wide range of adaptations, from the cryptic hide and lunge predators, such as scorpion fish, to the sinewy, fast moving moray eels, to the sleek fast swimming jacks, that look much more like the classic fish design. Finally, some species of fish are omnivores, feeding on a wide range of food sources, including invertebrates, algae and detritus