Damselfish have flat oval bodies, a short head and a particularly protractile small mouth. The pectoral fins are broad and brush like. The first ray of the ventral fin is stringy. The tail fin is forked and pointed. Adults are dark brown or almost black whereas juveniles are a lively, almost fluorescent, light blue.
This species tends to form thick shoals that swim near coastal rocks formations and above reefs. Reproduction takes place in the summer (from May to August). The males mark-out a territory and carefully clean an area of rock where the female lays a number of sticky eggs. The male then guards the eggs until they hatch. The diet of a damselfish can include small crustaceans, plankton, and algae.