Algae serve as the food base for lots of species, however when left uncontrolled, can outcompete corals for space and sunlight eventually smothering them.
Surgeon Fish (Prionurus laticlavius), found in large schools over shallow areas of coastlines, play a very important role in the marine ecosystem because their constant grazing on algae prevents it from smothering and harming the corals, ensuring the reefs remain healthy.