I just didn't have any of this "brown gunk" on the bottom for about the first two months the pool was open. Then after reading on here, I started maintaining slightly higher FC levels. When I raised the FC, it was almost overnight that the gunk appeared. I had never had algae that I know of so I don't think it is algae. The water has always been sparkling clear, but the brown dusty stuff on the bottom makes the pool look nasty. Vaccuming just seems to stir it up. The pool looks spotless after vacuuming b/c you can't see the brown stuff (it mixes back in with the water) I have no way to vacuum to waste since I have a venturi type vacuum with a debris bag. It goes right through the debris bag. My filter does catch some of it before it settles back out, but no where near all of it. It will start settling again within a day. Maybe you are correct that it is just normal "stuff", it just seems odd that it seems to increase with FC levels. It sounds as though I may just have to vacuum every day to keep it stirred up. Thanks for your help Anna.