re-circulating system done easy: I just connected both of my waterfarms, with a cheap $15 water pump in the extra reservoir (rubbermaid tub outside of the cabinet), the pump continuously feeds into the top of the waterfarms, and the solution returns to the reservoir (water seeks it's own level) ... my waterfarms still used air pumps to drip thru the rings, (became it's own backup system), in case a pump would fail, my plants will be fine ... (look close, see why Mylar sucks ?) ... :jointsmile: