Hi, I have a new establish tank cycled for weeks, NH3 is now gone, and I measured NO2 2 days ago, the reading was 1.6mg/l ( it has been staying at 1.6mg/l for quite a long time ), yesterday I measured it, it was 0.8mg/l, today I measured it, it dropped to 0.3mg/l, why it peak for so long and it drop so fast? I did'nt perform any water changes, except for evaporation and I add water in.