An Underwater Garden

How Are Coral Reefs Formed?	......
Coral polyps	Reefs are formed by coral colonies of tiny animals called coral polyps. Each polyp is a tiny, worm-shaped animal that secretes a material called calcium carbonate.
	The carbonate hardens into a lime cup around the polyp's soft body. The hard material forms over many years by millions of polyps to make a coral colony.
	Coral colonies and other organisms build the coral reef. Coralline algae cement various corals together and organisms such as tube worms and mollusks donate their hard skeletons. Together all of these organisms build many different types of beautiful coral reefs.