Earlier in this thread had posted a diagram of what I ultimately wanted my filtration to look like. In that design a had a protein skimmer because I have used AquaC protein skimmers on reef tanks in the past and I thought that their spray injection design would work on a freshwater pond. So I got one and hooked it up...
As you can see, the spray injector did create plenty of bubbles but in freshwater there was not enough surface tension for the foam to rise up the wide diameter foam tower. So I made a small modification and raised the spray injector above the level of the collection cup. This allowed me to set the water level just below the collection cup...
The result was that I was able to collect a lot of very wet skimmate...
Next I used a piece of an old gravel vac tube that just happened to fit just right to extend the height of the tube in the collection cup. This allowed me to increase the flow to the protein skimmer. The added pressure resulted in a much better quality foam...
For some reason, on a pond the foam production increases greatly at night...
So the final part of the story is that I sent these pics to AquaC. They replied that they had actually tested a freshwater pond version of their protein skimmer years ago and had good results but being a saltwater focused company they weren't sure if there was a market for them so they never pursued it. Well long story short, they are building me an AquaC Pond protein skimmer to test out on my pond. I'm looking forward to seeing how it performs.