Herbivorous fish are like cows of the sea; they graze on algae and plankton, deriving nutrition from plant substances while removing bacteria and algae from surrounding areas. Herbivorous fish primarily live on coral reefs; they maintain a proper balance between corals and microalgae that live on reefs and minimize competition among species, such as macroalgae and corals.
With the increasing threats to coral reefs, such as disease, predation and global warming, herbivores play increasingly important roles in maintaining the health and vitality of coral ecosystems. Fish, such as clown fish and surgeonfish, are herbivores that feed upon coral, plankton and algae in tropical ecosystems. As with other types of reef fishes, these organisms are brightly colored, and share many biological characteristics, such as gills and backbones. They have special digestive systems with complex cell walls, and rely on pharyngeal teeth and beak-like mouth structures to chomp and chew tough fibrous strands of kelp, seaweed and other plant materials. These fish use mechanical, chemical or enzymatic digestive processes to digest food after consumption. Mechanical digestion uses pharyngeal gills or stomachs to grind and shred algae while chemical digestion involves the interaction of chemicals and digestive enzymes to perform the task of acid lysis. Lastly, enzymatic digestion is achieved using microbial fermentation.