I guess I should preface that I've been looking on here for a while, tried almost everything, but I'm finally giving in and making an account. My tank is about a month old, and I stupidly bought fish and the tank the same day without knowing about the nitrogen cycle. Now that I've been progressing very carefully with the fish (7 danios and a mystery snail) the ammonia has lowered to 0, nitrates at 40, but my nitrites are off the scale. I have the precious master test kit, so I know it's accurate. I just bought it so it's not out of date. So I need help, not sure if soon or not because this has been happening for about a week. Nitrites are above 5 ppm ( test only goes to 5) To attempt to fix this I have: -Done multiple vacuumings (at least 10) -a 90% water change which lowered the nitrites for all of 5 minutes and went back up -added fluval cycle to the tank -reduced feeding to lower ammonia -tested tap water (0 nitrites) I'm running out of ideas here. I haven't changed the filter because I'm scared it'll start the cycle over again. The fish seem to be taking it well though. I've had no problems and they look great, but I still get unnerved about these levels. Am I missing something?