Apparatus for the treatment of liquids, including waste liquids, by aeration. The apparatus has a propeller, a motor and a leg extending between the motor and propeller. The leg includes a shaft coupled to the motor, the shaft driving the propeller. An outer housing of the leg generally surrounds the shaft. Air is drawn into and through the leg on rotation of the propeller within the liquid and is discharged into the liquid generally adjacent the propeller. In the improvement of the present invention, the shaft is solid while a tubular cantilever is supported at one of its ends within the outer leg housing in surrouding relation to the shaft. The tubular cantilever extends from its supported end away from the motor. Bearings support the shaft via the tubular cantilever at spaced locations along the shaft and cantilever.