I have a 30g tank with 2 Marineland 200 filters (200 gph each filter) with ammocarb in the media slot. I have 5 cichlids (2 SA and 3 Africans) my tank has been set up for about 3 months with the same fish the entire time and have had no problems. Two days ago I did a water change and checked my water and my nitrite levels are about 3.0 and my nitrate levels are safe at about .2. My ammonia levels are safe as well. I have been doing daily changes to try and lower the nitrite level and bought some Microbe-Lift Nite-out II. I just checked my levels again today and they are the same. What else can I do to lower the nitrite levels. Up until the levels were high I did weekly changes of about 5% and have never had this problem. I have no live plants and am using gravel as a substrate.