There are many types of corals. Some are hard and some are soft corals. The names were given because of the similar appearance of the different types of corals. The difference between hard coral and soft coral is that soft corals are usually very colorful and hard corals are usually white, taking their color from their limestone skeleton. Hard corals also produce an outer skeleton of calcium carbonate.
Soft corals have a skeleton of horney tubes, spikes and rods.
These are buried inside the animal s body. Coral reefs usually grow in the warm tropics. Calcareous algae help the coral reef to grow, like stony coral. These plants produce calcium carbonate, and it helps the reef stay together. These stony corals help to form coral reefs.