The present invention discloses a fish tank with a function of discharging waste water from a bottom thereof. A side at a bottom of the fish tank body is provided with a drain hole which is connected to an L-shaped tube, such that by rotating low the L-shaped tube, the waste water at the bottom of the fish tank can be discharged and by rotating high the L-shaped tube, the fresh water can be stored in the fish tank. Moreover, by providing a V-shaped transparent baffle, a bottom mud plate, a submerged motor and a breeder box which is hung up outside the fish tank, a closed food chain system is formed in the fish tank, allowing aquarium breeding to be simpler and easier.
