Hi aquahealth...
My fish tank at home, was 3 ft by 9 ft long. My water returned to one end, and the SLO was at the other end. I never had a problem with the solids making their way to the drain. The fish seemed to keep it stired up enough.

At one point, I had about 300 fish, that most of were over a pound. The swirl filter, that I had made out of a 55 gallon barrel was geting a work out.

Bsfman already mentioned fish density. The food you use, can make a differece on the amount of solids too.
I normally use purina aquamax feed.
When I had the 300 fish, I was raising 200 of them for for two different people. They were buying feed for me to use. One of them went 'cheap' and bought a bag of purinia 'pond feed'. It must of had more fillers...?..I had a lot more solids.


You mentioned you wanted pristine clean water. I don't mean to discourage you...If your picturing water like in an aquarium, it most likely won't happen.
I've seen in person, about a dozen different AP systems. They were all mature and had a varing amount of a tea stain to the water.

I'm helping my friend maintain 5 seperate systems. Like bsfman mentioned, the one with the lightest stocking , is the clearest. It 'looks' very clear, but put it in a glass and hold it up, it's not like city water.

One of the guys here was using 'quilt batting' in a mechanical filter. I remeber he said that made a big difference.