What differentiates the Cluster morphology for SPS corals is the tightness
of the branches. Much like the Bushy type, Cluster
corals have branches originating from a central point. However, cluster
branches thend to be very thick and sturdy. Certainly some of the most
commonly kept corals are of the cluster type, including what may be one
of the most popular species of SPS coral, the Acropora
Millepora. Advanced reef keepers are able to keep many corals in this
morphology with stunning bright colors, while the slow growth of certain
species make them very desirable to collectors.