A method for cleaning waste water is provided whereby the waste water is led through a throughput tank having filler materials to which aerobic microorganisms are adhered and wherein the throughput tank is ventilated with an oxygen-containing gas. As filler materials, materials are used which have a specific weight approximately equal to the specific weight of the waste water whereby the filler materials are suspended in the waste water. The inflow of the waste water into the throughput tank and the ventilation of the throughput tank is affected from bottom of the throughput tank and in such a gas amount that the waste water and the filler bodies suspended therein are mixed and the microorganisms on the filler bodies are supplied with sufficient oxygen. The device has a throughput tank with a tank bottom, a tank wall, wherein the inflow connecting pipe and the ventilation arrangement are arranged on the tank bottom and the outflow connecting pipe is arranged at the upper area of the throughput tank.