Alright I will start with tank specs, its a 50 gallon(48x12.5x20), I run a tetra whisper EX70 and an AC20(had from an old 10 gallon). I started my cycle about three weeks ago by dosing with pure ammonia to 5ppm, about a week and a half ammonia dropped and nitrites rose. Ammonia would drop to about .5 ppm from 4ppm in about 24 hours. I would dose up to 4 ppm whenever i saw it drop that low. Nitrites have held steady at 5ppm the whole time. Nitrates have held steady at about 40ppm. I dosed up to 4 ppm ammonia two days ago and it looks to only have dropped 1-2ppm since then. I am wondering why the tank isnt processing it as fast as it was before. Any thoughts?