Plants, plants, and more plants...
Filteration is not an issue. At that volume you really only need areation and plants. Areation can be a couple of fountains or air diffusers. The waterfall feed by a skimmer will use getted clogged and need constant attention, but will look really sweet. The air diffussers are a 1/3 -2/3 hp and have self-weighted air hose. You could run a handfull of these throughout the pond. A compressor is used to operate them and is good up to 20' depth.
Filteration is not an issue. At that volume you really only need areation and plants. Areation can be a couple of fountains or air diffusers. The waterfall feed by a skimmer will use getted clogged and need constant attention, but will look really sweet. The air diffussers are a 1/3 -2/3 hp and have self-weighted air hose. You could run a handfull of these throughout the pond. A compressor is used to operate them and is good up to 20' depth.