My new DIY air-lift pond is finally done. Woo hoo!!
I started this pond Spring 2009. It's all DIY and I am not as young as I used to be, so it took a while. The beauty of this pond is that while the shower filter and waterfall do have a small pump (1800 gph), the rest of the water in the filtration is not moved with a water pump, but with air. It's called an air-lift system. It works by introducing air bubbles into a return pipe, 5' below water level. As the air bubbles rise, they push a lot of water ahead of it. I have a Dolphin AV-150 (140 watts) air pump on the air lift header and it moves 9000 gph.
The pond is 7' deep with block walls and a liner. The walls are filled solid with concrete and rebar. The skimmer carries water to a barrel behind the wall, and a 1800 gph mag drive pump pushes that water to the shower filter full of oyster shells (to correct my pH/kH problems) and to the waterfall. The bottom drain takes water to the 275 gallon tank, a mechanical filter barrel with matala filter mats inside the tote tank, then to a fluidized filter bed (bio filtration) and finally to the air lift header and barrel and then return to the pond via two 4" pipes located below water level.
The total volume of this pond is 4660 and it will house 5 of my best female koi.