When I did my water change yesterday, the water that I took out from the display (my detritus settled in the sump before rollermat installation, so that water was obviously discolored), it was COMPLETELY clear. The clarisea rollermat polishes the water to an astonishing degree. Absolutely 0 discoloration.Freshwater fish excrete most of their nitrogen as ammonia from the gills. I think saltwater fish are the same but I'm not 100% sure. If you don't have a lot of uneaten food then most nitrogen is going to be coming from the gills and not affected by mechanical filtration.
The Hirayama paper on waste accumulation found that there wasn't much of a relationship between filter flushing interval and nitrate levels:
But there were differences in DOC which inhibit growth at levels ~125X lower than nitrate: