does your water have chloramines? I really don't want to post about something I'm not 100% sure about, but I had to deal with chloramines for a week or so, and I'm pretty sure that a byproduct of breaking down chloramines is ammonia. I think the majority of it should evaporate eventually, but a good cycled tank should handle the rest. I just ask because my tap registered at 1 ppm's of ammonia and it was because the current place I was in had chloramines in their tap, and I had a minor freakout involving wondering if I was going crazy because no matter how many water changes I preformed the ammonia wouldn't go lower than 1.