Many others have a dendritic growth form, creating a fan shape or elaborate tangle of tree-like branches. At least 14 species of black corals are currently known from Hawai i. Black corals are found in all oceans, but are most common in deep water habitats of tropical and subtropical seas. Colonies are frequently found near drop offs, terraces or ledges that are swept by swift currents. Their abundance may be related to available space in favorable conditions. Colonies that occur in shallower habitats are usually found in shaded areas or where light penetration is reduced.
Black corals are carnivores.
Firmly attached to the seafloor, colonies are swept by swift currents which move animal plankton over the polyps. The fan-like growth patterns that characterize colonies of some species are thought to be an adaptation for efficient feeding in a unidrectional current flow. This means they are not limited to sunlit reaches of the reef and so often occur in caves and under ledges, as well as at great depth. Relatively little is known about the life cycle and reproduction of black corals. Like other cnidarians, black corals have life cycles that include both asexual and sexual reproduction.