The blue devil is often confused with the yellowtail damsel because they both look so similar to each other. The main differences between the two species are that the blue devil has yellow on the mouth, face, and into the belly region and tail. It also has a black lightning stripe going backward from the eye. A blue devil can be kept in groups in a large enough aquarium, although it is best to have only a single male in the group.
This fish is raised commercially, and it is almost always available in your local fish store. It will spawn readily in an aquarium, and the males may become aggressive, especially if they are spawning. A blue devil is often used to begin cycling a new aquarium, but this is not a great idea because it can claim the entire tank as its territory, and get very aggressive toward any other fish as they are introduced into the tank.
Feeding a blue devil is not a problem because it will eat pretty much anything. In addition, it will graze on algae and other foods that arise naturally in a tank. It is completely reef-safe, and will not bother any invertebrates.