Snails Hermit crabs,
Most do not appear to, but there is at least one species that does. This species in question is known as the Parrot Fish, which feeds on coral and a wide variety of other reef organisms.
Angelfish eat algae, some coral, smaller fish, brine shrimp. Angelfish are omnivores.
Many things may eat coral and algae, certain types of snails, hermit crabs, blennies, and sea stars will eat different types of algae and detritus
Flamingos ducks
Parrot fish do and other sea creatures
sea anemones protect the clown fish, [as seen in finding nemo], and coral eats algae; mostly. :]
Predator.
Amoeba eats other organisms and smaller protists
Some, like suckers, eat algae and minute organisms. Others, like bass and trout, eat smaller fish and insects.
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dogfish, sea urchins, walrus, pizza(jk) and seaotters
alligator eats it