My tank seems to be in the final stages of cycling. The nitrites have been steadily declining over the past few days and are now between 0.1 and 0.2 ppm. However, the ammonia has been stuck at 0.25 ppm approximately for the past couple weeks. Is this normal? I was thinking that the ammonia was supposed to be zero by the time the nitrites were declining like that but now I'm guessing that maybe I was wrong.