Within the reef exists a complex food web in which nothing goes to waste. Animals such as conch, sea urchins, and surgeonfish graze on algae, thereby preventing it from overtaking and killing the coral. Huge eyed squirrelfish feed along the reef at night and help keep the grazers in check. Sea fans and sea anemones wave back and forth in the water column, using their tentacles to catch particulates and tiny organisms floating in the water. Other reef animals eat the coral or the mucus that coats it.
The coral reef ecosystem displays a complex interdependency of organisms. Some depend more on each other than others and develop symbiotic relations. The corals and zooxanthellae are one example of a mutually beneficial relationship. Another example is the cleaners and their hosts. Organisms such as the scarlet banded shrimp and neon goby "clean" other organisms by removing parasites and food particles from their gills and mouths. The cleaners get food while the host organisms stay free of potentially harmful parasites.