Definition
Stony coral, also known as hard coral, are the primary reef builders in the ocean. They are characterized by their hard, calcium carbonate skeletons. These skeletons provide the structural framework for coral reefs. Each individual coral animal, called a polyp, lives within a small cup in the skeleton. They can form massive colonies over hundreds of years. Many stony corals have symbiotic algae, zooxanthellae, living in their tissues.