The numerous species of saltwater fish eat different diets, ranging from carnivorous (meat eating) to herbivorous (plant eating) to omnivorous (both plant and meat eating). For marine fish in captivity, owners should research the proper diet information by species. Commercially prepared foods, feeder fish and the algae blooms in mature tanks are common food sources for different species of saltwater aquarium fish.
From tiny zooplankton and kelp to crustaceans and all the fish species, every living creature in the ocean has predators or culinary opportunists waiting to turn it into a meal. Some species of sharks are among the largest fish, and these notoriously voracious predators have been found with everything from human body parts to tin cans and driftwood in their stomachs. Of course, sharks are on the unusual end of the culinary spectrum, and most saltwater fish have much more reasonable diets.
Some saltwater fish have very specialized food preferences for which they have adapted specific physical traits. For example, the parrotfish feeds mostly on coral as a means of getting at the algae that lives inside the coral. The coral itself is chewed until it is ground into sand, thanks to the parrotfish's beak-like jaws, which are strong enough to crunch through even the hardest corals.