No. I've heard bio-balls produce nitrates, but when you stack live rock rubble up in your sump I can't imagine it not trapping detritus too. Actually, I know it does, because I have a bunch of live rock rubble in my sump, and it has detritus in there. I imagine it is contributing to nitrates just as much as bio balls do. I've put a powerhead in my sump and it seems to be keeping the amount of detritus down and the water clarity isn't affected at all. Skimmer seems to have produced more gritty, nasty skimmate over the last week too so I think the powerhead helps. Nitrates still through the roof though. I had a piece of LR with a small twig sticking out of it which I removed today (one of my original pieces of LR, always though it looked cool)- the twig may have been breaking down and producing nitrates, so we'll see if it helps.