The polyps on rock : Briareum, Knoppia, Pachiclavularia, Zoanthus...

The polyps on rock have one thing in common: they all live in colonies, each polyp is attached to the neighbouring one. This kind of colonial (or social) life differentiates them from mushrooms on rock that live in solitary (or in a non-social group). Such is the case of hard corals Briareum, Pachyclavularia etc and the famous colonial sea anemones - Zoanthus. These corals are all rather easy to maintain in reef aquariums, offering a nice range of colors and adapting well to nano-aquariums.