small aquarium fish of the carp family, Cyprinidae, native to the White Cloud Mountains (Pai-yün Shan) of Kwangtung province, China. The white cloud is a slender, hardy fish, about 4 cm (1.5 inches) long. It is greenish brown, with a silvery belly and red patches on its fins. On each side from head to tail, it has a gleaming stripe, brilliant blue in the young fish, golden in the adult. A rather popular fish, the white cloud is unaggressive and easily bred in captivity.