I've had my 75g setup for three weeks now and have been letting it cycle but my ammonia hasn't dropped yet. It's at 0.25ppm and I know you're supposed to wait till it's completely at 0. The Nitrites and Nitrates are both at 0, pH is at 7.6, and I do a 10 gallon water change every 3 or 4 days. Right now I have a 2in fire mouth and 5in pleco that have been in there since day one because I moved. I'm waiting to get an oscar but this ammonia won't drop. Any advice on what to do?