The blue damselfish, scientifically known as *Chrysiptera cyanea*, is a small marine fish commonly found in the warm waters of the Indo-Pacific region. They typically inhabit coral reefs and are known for their vibrant blue coloration, which can vary in intensity. These fish usually grow to about 3 inches in length and are popular among aquarium enthusiasts due to their hardiness and striking appearance. Blue damselfish are territorial and often establish their own areas within the reef. They primarily feed on algae, plankton, and small invertebrates. Their social behavior includes forming small groups, but they can be aggressive towards other fish, especially during breeding seasons.