Coral is a part of the phylum Cnidaria, which is a large generalization, but also distinctive. The Coral and other cnidarians have a mouth, or mouths, that open into one big body cavity. Coral does not have a true digestive system, so the cavity opening acts in its place. After the food is broken down, the nutrients are sent through the rest of the body as food. There is also no excretory system; therefore the waste is sent back through the mouth or secreted into the surrounding water. Coral can be found in a number of places around the world. They range in shape and size and forms.
Most Coral have tiny living organisms that live in their tissue. Because of these organisms, strong lighting is needed in the saltwater aquarium in order for the coral to survive. One thing to be aware of with some species of Coral is that they can self populate, so you have to watch it so that it does not overtake the tank. These algae-like creatures provide the coral with oxygen and other nutrients that are produced during photosynthesis. Coral are often able to live in the same tank as other corals, but it is important to make sure that they are not in close proximity of each other.
