Video: After many tries and many fails, including commercial filters and eheim pond filters and DIY filters that could not keep up with my ducks, I have finally found the ultimate solution. I have added a 30 gallon biological pre filter tank stocked with floating water hyacinth and submerged anacharis to process large amounts of nitrogen and co2 in the water. All of it screened off from the top. This biological pond drains into a short stream followed by a shallow gravel pond. The shallow pond increases natural UV exposure to the flowing water. Finally that water drains through a small waterfall to the main pond where the pump sucks it through the mechanical (foam pad) filter. I am on day 3 of installation and the water has already become noticably clearer. I would love to hear more ideas. Thanks!