High Quality Content by WIKIPEDIA articles! The habitat of deep-water corals, also known as cold-water corals, extends to deeper, darker parts of the oceans than tropical corals, ranging from near the surface to the abyss, beyond 2,000 metres (6,600 ft) where water temperatures may be as cold as 4°C. Deep-water corals belong to the Phylum Cnidaria and are most often stony corals, but also include black and horny corals and soft corals including the Gorgonians (sea fans). Like tropical corals, they provide habitat to other species, but deep-water corals do not require zooxanthellae to survive.