[Ebook] Encyclopedia of Aquarium & Pond Fish – Directory of Marine Invertebrates – Corals
Corals form the centerpiece of any reef aquarium. A coral is a colony of linked organisms called polyps. In stony corals, which form the foundation of the reef, the polyps have a hard body casing of calcium carbonate, while the polyps of soft corals are supported by a less rigid calcareous structure.