What Is Coral?

Coral is often mistakenly believed to be a rock or a plant. It is really made up of tiny fragile animals called coral polyps. Coral polyps are spineless animals that range from the size of a pinhead to a foot in diameter. The polyp builds itself a hard, cup-shaped skeleton using calcium carbonate from the water. The skeleton protects the polyp's soft, delicate body. When we say "coral" we are really referring to these animals and the skeletons that are left behind when they die. One branch or mound of coral is covered with thousands of coral polyps.

There are hundreds of different species of coral but they are usually classified as "hard coral" or "soft coral".

Hard corals are the ones who build the reefs. Their skeletons are made of calcium carbonate, a.k.a. limestone, which is hard and turns to rock eventually. These corals need tiny algae called zooxanthellae (zo-zan-THEL-ee) to survive. Below are some examples of hard corals...

Brain Coral=

Elkhorn Coral=

Soft corals often resemble plants or trees. They are soft and bendable, and do not have stony skeletons. They grow wood-like cores for support and fleshy rinds for protection instead. They are referred to as non-reef building corals and do not always have zooxanthellae. Soft corals can be found in both cool, dark regions and tropical seas. Below are some examples of soft corals...

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