A sea fan, or gorgonian, is a form of sessile colonial
cnidarian, similar to a sea pen or a soft coral, found in tropical and
subtropical seawater. Individual tiny polyps form a colony that is
erect, flattened, branching, and reminiscent of a fan. A colony can be
several feet high and across but only a few inches thick. They may be
brightly coloured, often purple, red, or yellow.
The main structural skeleton of a sea fan colony is formed from a flexible, horny substance called gorgonin,
with living polyps covering the surface. Unlike corals, sea fans do not
attach themselves to a hard substrate: instead, they anchor themselves
in mud or sand. Each sea fan polyp has eight tentacles which catch plankton
that is consumed. The "fan" is often oriented across the prevailing
current to maximise water throughput and hence food supply. They may
also contain algae which photosynthesise.
Sea fans are classified in the phylum Cnidaria, class Anthozoa,
alongside the orders Alcyonacea (soft corals) and Pennatulacea (sea
The Pygmy seahorse makes the sea fan its home.Information from Wikepedia - http://en.wikipedia.org/wiki/Gorgonian