small tupperware container small plastic bottle w/ lid small powerhead diy co2 bottle w/ airline+airstone
attatch the intake of the powerhead to the tupperware, drill holes in tupperware lid to act as a filter. fill tupperware with filter materials. attach out flow to bottle cap, screw cap on lid and place over the bubbling co2 airstone to capture the bubbles.
the bubbles get caught in the bottle and churned by the powerheads out flow.