Ammonia After Cycling

[kara huels]

I did a fishless cycle using beneficial bacteria and dosing with bottled ammonia. The cycle happened as normal and now the Nitrates and Nitrites are finally at 0ppm. However, for some reason after they both hit 0ppm my Ammonium went from 0ppm to around 1ppm. What's going on? Any help would be appreciated. Thanks!