Parrotfish are named for their dentition, which also is distinct from that of other labrids. Their numerous teeth are arranged in a tightly-packed mosaic on the external surface of the jaw bones, forming a parrot-like beak with which they rasp algae from coral and other rocky substrates (which contributes to the process of bioerosion).
Although they are considered to be herbivores, parrotfish eat a wide variety of reef organisms, and they are not necessarily vegetarian. Species such as the green humphead parrotfish (Bolbometopon muricatum) include coral (polyps) in their diet.
Their feeding activity is important for the production and distribution of coral sands in the reef biome, and can prevent algae from choking coral. The teeth grow continuously, replacing material worn away by feeding.
One parrotfish can produce 90 kg of sand each year!!!