Blue Devil Damselfish
The Blue Devil Damselfish Chrysiptera cyanea is an enduring favorite of saltwater aquarists. A lively fish sparkling with a rich sapphire blue coloring and a bold personality, it brings the aquarium to life. It only grows to about 3 1/3 inches (8.5 cm) in length, but many folks like the purity and beauty of this brightly colored fish. It is one of the most popular of the damselfishes.
This species is dichromatic, with distinct color differences between the adult male and female. Those available in a pet store may often be juveniles that have not yet come into their adult coloration. As they mature, males originating from across most of their natural habitat, develop yellow-orange tail colors and sometimes yellow on the nose. Those males originating from Japan and the Philippines, however, are all blue with dark margins on the fins. Females are similar, being the same bright blue, but they gain a black spot at the base of the hindmost dorsal ray and the fins are clear. These fish are known by a number of descriptive common names that reflect both their color and behavior including Blue Damselfish, Blue Devil, Sapphire Devil, Sky-blue Damsel, Blue Demoiselle, and Orangetail Damselfish.