Beasts

We have a half acre pond in our backyard in which I am trying to develop a more complete ecosystem. It currently has a large population of mature blue gill and catfish. Over the past 3 years I have planted lilies, lotuses, rushes, Potamageton and Vallisneria gigantea. As they fill in the shallow areas I hope to encourage the blue gill breeding and fry survival rates to the point where I can introduce large mouth bass and provide them with a food source.
I currently aerate 24/7 through the warm months and use no dyes or herbicides. We feed pellets once a day just to supplement the food supply. My goal is to reach a point wher the pond is self-sufficient in that it requires no food inputs and stays clean and clear with just the aeration. (Can you imagine the filter which would be necessary for what I calculate to be more than 5 million gallons of water?! Especially with a flock of domestic geese using the pond as well.)
My question? Are there folks in the audience with experience with such a project? Has anyone ever created a bog system to help filter their pond? Any thoughts, comments, suggestions. etc. would be appreciated.
Beasts