The medaka, also known as the rice medaka, is a species of fish in the family medaka and genus medaka. The body of the medaka is long, flattened, with a straight back and a round and narrow belly. The head is wide and flat. Small mouth, upper position, transverse fissure, longer lower jaw. Eyes are large, located on the upper side, and the distance between the eyes is wide and flat. The top of the head and gill cover are covered with scales. The dorsal fin is located at the back of the body. Qingchui is a small freshwater mid to upper level fish. It lives in ditches, paddy fields, ponds, and aquatic plants along rivers, lakes and reservoirs. Xi Qun swims in still and slow-moving water areas.

The medaka is one of the more popular pet fish. In recent decades, it has been widely used in the fields of developmental biology, molecular biology and toxicology. It is one of the organisms to study the proliferation of vertebrate germ cells, genetic mutations, diseases and toxic effects of pollutants.