As the biomedia or mechanical media gets plugged/gunks up, slight adjustments need to be made to flow with a ball valve, and occasionally, I dump the lava rock and rinse it off. If flow is too high, water can overflow the Tee in the horizontal pipe, or if flow is too slow the foam will bypass back into the pond. As with any sort of filtration, maintenance is required.
As far as clear PVC, in Milwaukee I get it from Modular Piping Supply, but I would go with standard PVC if making another. The clear pipe is expensive, and sunlight can create algal growth in the clear vertical pipe, causing need for extra cleaning. I used it at first, because I wanted to see the action, but that in the end, not really needed.
If I made another, I'd also make it taller for a better cascading action.
I saw one made for a large pond on youtube that was taller than a garage, and the foam was incredible.
A few years back, I did experiments in the lab, weighing dessicated skim waste, and also compared microbiologic life compared to life in tank water.
The dessicated foam was 8-10 times heavier than weight of dry solids dessicated from straight tank water.
And bacterial/protozoa counts were somewhat in the same ballpark.
above skim waste left, tank water on right.
Below, skim waste was too thick for the micron filter, so dilution of the skim waste, and extrapolation was used to determine end weight.
dessication process below
Duanes, that was a very interesting video. So water cascades through the lava rock as a W/D, and foams up at the bottom to some extent, and is skimmed off at the wye? I take it you have to re-tune the ball valve at the outlet regularly so you don't dump water out the wye, or have the foam pass the wye?