How long does water hold dissolved oxygen?

I've built a top drip system that recycles the water back to a main reservoir. Now for the way I set it up, I took a shortcut, that is now looking to cause me problems. The way the system is set up is I have all my 5 gallon buckets sitting on the floor. They all drain back to a "bilge" container, which pumps it back into a reservoir, where my air stones are, and then back out to the drip lines. Now, because I have 30 buckets, and them all trying to drain back to the same bilge container, the water flow is restricted, and does not flow back fast enough. This has caused the water level of my pails to come nearly to the bottom of my net pots. I've got a couple options, I could put a inline pump to pull the water through the lines, or I could ad air stones to every bucket and it'd be a classic DWC setup. I'm just wondering if the steady flow of the water is enough for DWC or if I'd need to put air stones in regardless. The pump option isn't so easy either, as I'll have to buy extra float switches and another pump as a safe guard in case water levels get to high in either container, wire up a bunch of relays, transformers and ac / dc converters (only float switches I can find that work with 1.5" of water are 12-24vdc). Any advice here would be greatly appreciated. I am somewhat new to this design, I've worked with ebb and flow in the past though. Thanks guys