I should have been a bit more specific. Whenever I do a water change I vacuum the substrate and live rock. I use the water I draw off to clean my Fluval 205 sponge filters. From time to time I slack off on maintainance and have to deal with higher than sugguested nitrates. It takes a while to get them down but it does work. If they are really bad, a big w/c and vaccuming are in order.