I have been running this new system for 3 months and all is going well. This system is made of recycled materials and hosts 11 koi fish and 1 plecostomus. The fish tank holds 180 gallons and the medium for the grow bed is locally sourced creek-bed gravel.
This is my first system ever and it took me a lot of research and imagination to figure out the right design. The method I chose is a continuous flow through the gravel with a single standpipe. The water exits the bed and splashes back into the fish tank below for aeration. No problems so far. We have gathered a surplus of melons okra beans corn tomatoes and tobacco.
As we live in the Sonoran Desert, temperatures may be extreme. That is why i chose a continuous flow system with a simple standpipe overflow. Electricity is consumed by a single pump which fills the gravel bed and aerates the fish tank at the same time. The fish tank is submerged in the ground for thermal mass and to slow any extreme temperature changes. It is not uncommon for the temperatures here to vary 40 degrees F from day to night. Also the fish tank is covered by the gravel bed and lumber box to prevent evaporative losses in the 100+ degree F summer temp. Everything transplanted so far has survived and thrived. Ammonia Nitrite and Nitrate levels are always close to zero. The PH is just above 7. And average water temp is 70 deg. F. I have placed an old wrench found in the desert directly in the gravel bed as a source of iron.
Please feel free to reply with any comments suggestions.
Thanks for the pointers Jon.