Abstract: An apparatus and method for pumping air in which ambient air is mechanically filtered and introduced into a stream of water circulating in a closed path and driven by a water pump, the air-water mixture being directed to an air separation chamber in which the air-water mixture is forceably impinged against one wall of the chamber to cause frothing of the mixture. The frothing mixture rises through a reservoir of water in the closed circulatory path into an air plenum chamber above the water level, the air rising into said plenum chamber being water stripped of pollutants not removed by the mechanical filter. Air collects under pressure in the air plenum chamber, the pressure air being released through a suitable tube or duct and introduced into a tank of water such as an aquarium.