What Is The Difference Between Hard And Soft Corals?
Hard corals, also called reef-building corals, produce a rock-like skeleton made of the same material as classroom chalk (calcium carbonate). These skeletons and the various shapes of different colonies form the familiar structure of the reef. Hard corals rely on symbiotic algae (zooxanthellae) living within their tissues for nutrition and energy to build their skeleton. They must therefore live in shallow clear water to allow sunlight to reach the algae. Soft corals look like colorful plants or graceful trees and are not reef-building since they do not produce the hard calcified skeleton of many reef-building corals. However, soft corals do produce smaller amounts of calcium carbonate that help them keep their shape. Soft corals can be distinguished from hard corals by the fact that soft coral polyps always have eight tentacles, while hard coral polyps have multiples of six tentacles.
