Earlier in October I had the opportunity to do the tour at Growing Power's facility in Milwaukee. While everything together is very cool, I naturally left with more questions than when I arrived. The big question is what the recirc system they use is most like? Besides the biofilt from the plant beds; which is gravel, supplemented with compost, an primarily monoculture watercress, and strong aeration, the water goes up and comes down.
The raceways work out to 1 fish per gallon(somewhere in the 10000 gallon range), the water is totally opaque and they harvest truckloads of watercress. However the beds don't appear to be ebb and flow, just gravel beds with fill on one side and drain on the other end. I suppose since watercress is an emergent plant, it can handle being wet all the time, but has anyone ever seen, or used this technique? It seems to be somewhat like NFT, but I'm not real sure.
It would seem to be a relatively easy way to go, if you could do more terrestrial type plants, but like I said the AP systems were more or less monoculture.