Water is circulated from the breeding tanks to the biofilter with an airlift. Air is bubbled into the bottom inch of the lift tubes, bringing the water up out of the IBC tote into the biofilter barrel. This takes care of the pumping action, as well as the need for aeration. The lift tubes are mostly submerged, with less than 1′ out of the water. There is one air pump for all thirty 1000 liter breeding tanks. This is a high volume unit running at approximately 2 psi.