Hard Corals

There are two main types of corals: hard corals and soft corals.

Hard corals, like elkhorn coral and staghorn coral, grow in colonies and are often referred to as “reef-building corals.” Hard corals create skeletons out of calcium carbonate, a hard substance that eventually becomes rock. Overtime, this rock builds up to form the foundation of a coral reef and provides a structure upon which baby corals can settle. Hard corals depend upon tiny algae called zooxanthellae (pronounced zo-zan-THEL-ee) that live inside them. Together, they share a symbiotic relationship—the corals provide the zooxanthellae with shelter, and in return, the zooxanthellae provide the corals with food.

Staghorn coral (Acropora cervicornus) in Cordelia Banks, off the coast of Roatan, Honduras. Photo by CORAL staff
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