Hello Fellow Pond People! LOL! I have a 13K gallon pond, with a liner. It has a bog, with lots of plants, a waterfall that runs 24/7, two aerators that are solar, and is seven feet deep in places. It's 35x25 so it has lots of surface area. No mechanical pump. Because of suspended particles and tannins, I was thinking of putting in a filter. My budget is $400.00. I have eleven koi and comets. Some frogs now! There are a lot of trees shading the pond. What suggestions do you have for clearing up the water? I am not going to add any chemicals except clay to flocculate. There must be somebody who has had the resolution of a similar situation. I want to see my fish! Thanks. Tom.