OK, now it's my turn to ask a question. Everything in my 100 gal. tank is optimal accept for the nitrates which I couldn't seem to get below 40 way to high for Discus. I finally took everything out of my aquarium and really vacuumed the substrate when I took everything out I found how filthy it had gotten. I took out about 50% of the substrate then I found the ammonia had gone up to .25 but that went to zero after a couple of hours the Nitrates are still reading between 10 and 20 on top of my 4 filters I added air stones because I have heard that it will carry Nitrates to the top where they are then released into the atmosphere. I am still trying to get the Nitrates to 5 or registering 0. Does anyone have ideas? Oh, my tank is not over stoked and I don't over feed them.