What is the X in X-mas?
any of several slender tropical fishes of the genera Danio and Brachydanio in the carp family, Cyprinidae. Danios are hardy and swim actively about in schools. They are generally some 4-5 cm (1.5-2 inches) long. Several are often kept in home aquariums. Among these are the zebra danio, or zebra fish (B. rerio), a popular species with lengthwise blue and yellow stripes, and the giant danio (D. malabaricus), a striped blue and yellow fish about 11 cm (4 inches) long.