Pond Filter Box - 3 Sections: Screen medium cavity

I have a small pond using a TetraPond 550. My water feature was losing pressure with my original mesh bag solution so I designed something new. This design is actually based on work I did as Biosystems engineer 20 years ago at the Oklahoma State University Hog Research Farm. At the time we were using straw biofilters to clean out the odorous air leaving swine barns, this uses the same basic concept to work. Essentially it has 3 layers: The top layer is a simple screen which is designed to capture large debris like leaves and garbage. Most of the time you can simply remove this dump it in the garden and carry on. The second layer is for bacteria medium. I have mine filled with 9 nylon scouring pads. You could also fill this with printer poop, but you would probably just want to use PETG so it doesn't degrade as much (?). Really any medium would work as long as bacteria and stuff can live in it and help clean your water as it gets pumped through.The third layer is simply a void area