Quote Originally Posted by keith_r
so is this a hydroponic site or aquaponic?

just kidding..
but, ap and hydro are completely different animals.. with fish in the mix, added oxygen is essential... it's not just about what is "sufficient" for the plants, but the what is the optimum balance..
You make an excellent point. Fish typically need a minimum of 4 ppm DO whereas plants barely need 2 ppm DO. Therefore, wouldn't the fish being alive indicate we have enough DO in the system?

I don't have a high density system, but my AP setup has no aerators besides the agitation from the water return. 1 pump and that's it. The fish grow fine and so do the plants, even when I had the floating raft system.

Last point, aquaponics is hydroponics as far as the plants are concerned. Try, if you will, to illustrate just what a plant needs that is different in aquaponics than in hydroponics. AHA! (keep in mind the limiting factor for the DO is the fish not the plants as the plants needs about half as much DO as the fish to survive)