Floating raft

[urbanfarmer]

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)

[rfeiller]

without a doubt the bottom line is the nutrients needed by the plant does not change whether it is aquaponics/bioponics or hydroponics or does it? bioponics of any sort have mychorriza, fungi, bacteria, that aid in the absorbtion of nutrients by the plants whereas hydroponics does not offer these advantages and must rely on the correct pH for the proper absortion of nutrients?

[urbanfarmer]

Traditional hydroponics can have mycorrhiza whether intentional or not. With that said, have you ever seen mycorrhiza on your roots in aquaponics? I have not seen my roots show signs of it. Even so, that doesn't really change things. In hydroponics like we have or traditional hydroponics, the water flows across the roots pretty readily. As shown by research, the more water movement there is the lower the nutrient levels can get because the plant is still able to absorb the nutrients it needs.

None of this has any bearing on the dissolved oxygen levels.