Yeah, I also made a recirculating system. Water pump in the res, 1/4" line to the grow tub streaming water 24 hours. It's the only way to be sure everything stays moving.

Mine is just miniature compared to yours. 18 gallon res, 10 gallon grow, 10 gallons total water. 1 airstone in the res, and 1 airstone beneath each plant.

RO water has no PH buffers, so it takes only tiny drops to adjust up/down, but it potentially fluctuates more up/down by the same token. Think so anyway.