Soft corals are members of the order „Alcyonacea“, all belong to the subclass Octocorallia. The name "Octocorallia" refers to the fact that each polyp has eight tentacles. They are found mainly in tropical waters around the world in often strong varying environments. Soft corals lack the limestone skeleton found on their relatives, the hard corals. They live on coral reefs along with hard corals and have a swaying jelly- like body. As allready written, Soft corals are easy to distinguish by their eight tentacles on each polyp and have a feathery appearance, whereas hard corals have smooth tentacles. Some of theme produce hard skeletons but, because they have eight-tentacled polyps, are easy to be classified as soft corals.
Many soft corals contain zooxanthellae and so need a lot of light. On the other hand many of them, like the carnation corals, grow on the underside of reef ledges or shaded areas and don't require light. They usually must be fed to survive in the aquarium.
Soft corals are able to move, very slowly, by extending the tissues at their base. When their route crosses hard coral colonies they kill the polyps, leaving a white, dead path behind them. In reef aquariums, it is important to leave adequate space between different species of hard and soft corals to avoid problems with growth or aggression. Most soft corals grow rapidly in reef aquariums, and are relatively hardy corals for the inexperienced reef aquarist.