Theo, I've been to Cecil's numerous times. He uses 5 gal buckets with the bottoms drilled to let the water through. He puts the bio balls in the buckets, and has 3-5 buckets above each other in a line. He connected the buckets to each other with it looks like aluminum strapping screwed right to the buckets and about a 6" gap between each bucket. He dumps well water into them at the rate of 50 gpm, the water falls to a sump pit, then gravity feeds to his trout pond. It's called a "packed column" and he does that to aerate the water, remove any harmful gasses and also to get the iron to precipitate out from the water. I'll see if I can find a picture of it.
Some hatcheries do that on a much larger scale, using a concrete structure to aerate the water and to get the iron to precipitate out. One hatchery has to clean out their sump 2x/week, and their concrete sump area is about 12 feet square. That place is running 200-300 gpm through the system.
I found it. Here's his thread, some of the pictures are missing due to PhotoBucket screwing with their system.
https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=283273
