Here is the star of the show. It is the netting, tied in the center with heavy fishing line to the pen shaft. I figured it would be on my regular list of things to clean, but the rushing water takes care of it. If anything large goes down the stand pipe, the netting just moves out of the way.
On my other system with three stacked tanks, I have a vertical drop of 46 inches. It is a 1.5 inch pipe with 1.5 inch bio-balls inside. It is also quiet, but the bio-balls do not move out of the way when something large goes down the shute.