I've been doing a fish-in cycle (4 platys) for 8 weeks now. I have a 37 gallon tank, with the following test results: - Ammonia, between 0.25 and 0.5 - pH, 8.0 - nitrite, 0 - nitrate, 0 - temp 75 Shouldn't I see the nitrite/nitrates go up by now? I've been doing about 30% water changes once per week. Initially i was doing smaller changes more frequently but had a problem getting my ammonia levels up. I've changed the carbon filter once and need to replace it again this week. I haven't touched the other filters. I do vacuum my substrate once per week. Am I doing something wrong?