I started a thread like this some time ago, when the power went out in Darien/Downers Grove and I had some causulties. After looking for info online and talking to my trusted LFS guys, I was given the impression that the airstones or creating bubbles had limited oxygenation effects. I was refered to a article by Homes regarding this but I can't find it now. The general consensus from people who have been doing this for awhile, suggested prioritizing water movement at the surface for the purposes of gas exchange. Basically pointing a powerhead toward the surface of the water. I like the car battery idea for the purpose of long life, limited expense, and the ability to recharge it. That's my plan.