It is many marine invertebrates typically living in compact colonies of many identical individual "polyps".
Hard Coral is not a fish but, some small fish live in hard coral.
Fish aren't mammals...
butterfly fish, hard coral: brain coral or table coral
Most fish do not eat live coral as it is hard and not very nutritious. However, some fish, such as the butterflyfish and parrotfish, may nip at coral polyps or feed on coral mucus. These interactions typically do not harm the coral if kept in balance with the ecosystem.
No there are very few animals that eat coral because of their very hard shell. Some fish have hard parrot-like beaks and eat the coral, and some starfish digest the inside part of the coral.
There are many different kinds of animals in coral reefs and I couldn't possibly list them all here, but the general categories are: exotic fish, sea mammals (otters, sharks, dolphins, etc), turtles, and, of course, coral.
It is a hard coral
hard coral
Its coral fin not coral fan! Actually, it IS coral fan! Coral Fans, also known as sea fans, are more correctly called Gorgonians. They are colonial soft corals which grow in a "fan" shape and anchor in sand instead of on hard surfaces as hard corals do. Their primary predators are fish such as, but not limited to, angelfish and butterfly fish. They eat plankton which they capture as it drifts past them.
No, fish are not mammals.
Fish are not mammals, they are fish.
Some fish eat of the coral reefs, but they do not live on or in the coral reefs. But every fish living on or in the coral reef has a job to do that protects it from the intrudors.