Ok so I've been having this problem for about 3 weeks now in both my 90 gallon tank and my 10 gallon tank. My nirites and ammonia are at 0ppm but my nitrates are stupid high around 80-100 ppm. I've done 50% water changes. I always do them every 2 weeks. I just cleaned the filters out thinking that was it but it didn't help. Any advice would help. I've never had this problem the 90 has been up for almost a year and the 10 gallon around 4 months. I did add osmacote root tabs about a month ago could that be the issue?