A very good question. We're going thru a battle right now. Most advice on the board will tell you to reduce feedings, reduce lighting and add more circulation. There are chemicals out there that will rid your tank of the slime, but I wouldnt recommend them from my own experience, but others have had success with them. I wish I had better advice to give, but right now I feel like we're fighting a losing battle also. Trying to be patient. Try doing a search on red slime and you will get A LOT of threads to read. I believe most will tell you what I've already suggested, but I may have missed something while I was searching. Let me know if you find anything else, we're looking for ideas as well.