Abstract: The present invention is directed to an efficient aeration system for use in a pool or lagoon. The system employs a venturi nozzle structure for mixing air and water. With this nozzle, multiple air streams surround a water stream to promote effective mixing. The air water mixture is discharged into a long discharge pipe which extends the mixing time for the air/water mixture leaving the turbulent mixing zone of the nozzle. Small holes drilled in the upper wall of the discharge pipe permits smaller bubbles to escape along the pipe while larger bubbles which have not yet been broken are carried further down the pipe. Further, the discharge pipe of the present invention is made larger than the nozzle area in order to slow the flow of the air/water mixture when passing through the pipe.