It does seem to have some fun possibilities doesn't it. If I remember correctly there is a powerful suction drain at the bottom that circulates the water through the filter and that might take fish solid waste out but not the liquid waste such as ammonia. That would be a biofilter maybe. I'm just getting into this.
I do remember seeing pictures of a recyclable bio system for growing food and fish. As best as I can remember it was a long troth of water with fish in it. Laid on top of the water was a rubber mat. Maybe neoprene with slits in it to hold plants. The roots grew in the water where the fish ate the roots and took up the fish waste for fertilizing the plants. I have no idea if it worked out.
I am running a side experiment now similar to that in the pond. The container is planted with mustard spinach that has grown and is up about 2" at the present time. The bottom of the container is about 1" below the water line and has a dozen half inch holes in it so the water seeps up into the soil mixture. The planting material is 3 equal parts of potting soil, perlite and vermiculite.
