If your going to use a pump, put it on a digital timer set to 5 minutes on once per hour. Otherwise you build up heat in the res and you know where that goes.. Also, I've yet to see someone run an airstone in an auto pot res and not have PH issues. It not the same as hydro. If the res bothers you, get a paint stirrer for your cordless drill and give it a good stir every day or so. I stir once a week and I've had no problems. Nor have I since I began using auto pots three years ago and stirring is something I only recently do to be sure I keep the megacrop in suspension. I've never found algae in my res when cleaning them between grows, no signs of bacteria. And I use to use Seagrow, which is mostly organic.