Zoanthid sp. (polyps)
Zoanthids or zoos as they've been coined are fast growing colonial animals that have wonderfull color variations. They will colonize an area very quickly and create a beautiful low lying cover over rock between corals
Zoos will benefit from feeding of small particulate matter as well as from high lighting. They do best under medium currents and will proliferate in good water conditions.
Zoos have gained alot of popularity lately and there are so many kinds available it's hard to believe. They can be propagated through fragmentation and shared with other aquarists. The picture above happens to be one of my favorite colonies, and has doubled in size since the pics was taken.