Colonies usually form a light brown mass covered in darker small-diameter corallites (less than 5mm in diameter). An encrusting coral, aspect and shape of a colony largely depend on substrate surface (can be flat or boulder). Corallite density may vary dramatically.

Common, often home to fanworms and Christmas Tree Worms.

Tentacles are often extended during the day. Their retraction tends to cause a change of colour of the affected area, hence the English name given to this coral. The corallites and their septa barely emerge from the coral surface.

Tentacles immediately retract if approached too closely, which contributes to dramatically change the surface aspect and coral of the coral.