My Korallin slows down sometimes too. Make sure that you are removing any undisolved gas, as montie suggested. This helps mine out too. Also, I've found that using just the valve on the outlet to control drip rate works much better than using the line restrictor. The restrictor initially allows a much easier control of the drip rate, but the high alk/calc concentration in the effluent hardens the tubing and tends to make the line permenantly crimped, thus removing your control. patience is required too. I've found that mine takes a few days of fine tuning whenever I need to retune it. Taking a quick daily look at the reactor to make sure it doesn't have too much gas, is dripping at the correct rate, and is bubbling at the correct rate goes a long way towards preventing problems. I use a pump too feed mine, and that may prevent problems as well.