To go to an extreme, how about building a plenum system with a funnelled base and a couple of valves at the bottom so that solids would collect in a base container. The valves could be closed and container removed and only the volume of the container of aerobic environment would flow through the plenum, which might only be a small jar or something. A small closed loop in the plenum additionally could resist settling away from the container.
Or maybe a closed loop with an external removable canister? Then add to this a CO2 bottle and you've got yourself a super-reactor.
-Rogue