Polyculture of loach with grass carp, herring, crucian carp, carp, bream, silver carp, bighead carp and other fish has better effect. These fish usually live in the middle and upper layers of the water and have different living habits with loach. Complementing each other, for example, grass carp and bream mainly feed on plant food, while loach feeds on small aquatic organisms. This combination can not only reduce food competition, but also improve breeding efficiency. In addition, it should be noted that loaches and goldfish should not be mixed because they have different requirements for water quality. Loaches need to live in waters with mud at the bottom, while goldfish need clear water and frequent water changes. Loach is widely distributed in China, Japan, North Korea, Russia and India along the coast of Asia. It inhabits the bottom of still water and is often found at the bottom of lakes, ponds, ditches and paddy fields.