The Yellowtail Damselfish, also known as the Yellowtail Blue Damselfish, Yellowtail Demoiselle, or Azure Damselfish, is bright blue with a tail of energizing yellow. (Some call C. parasema the Azure Damselfish, however, in the aquarium trade, the Azure Damselfish is considered to be C. hemicyanea.) It has an elongated body with a slightly-arched dorsal profile matching that of the ventral contour. It is brilliant blue in colour with dark-centred scales. A few dark lines cover the head and cross the large eyes. The caudal peduncle, together with the majority of the caudal fin itself, is bright yellow and this colour encroaches a short distance on the body of above the anal fin. The rear portions of the dorsal, anal, and caudal fins are uncoloured.

The Yellowtail Damselfish is a good choice for beginners since it is less aggressive and does not need as large of a tank as many of the other damselfish. It can be kept in small groups, and prefers to have many hiding places and peaceful tank mates. It will grow up to 2.5 inches. 

It will ignore invertebrates in the aquarium and feed on zooplankton and algae.  A varied diet of meaty items such as mysid shrimp and vitamin-enriched shrimp should be offered.