i would think that would be a bad thing? is your tap water showing ammonia? how are you testing it? could be a bad test kit. i dont think that tap water should have a detectable amount of ammonia. i could be wrong though.
uh if your tap water has Ammonia you should contact your local water company. Your tap water should not have ammonia EVER it is unsafe and you could get very sick. Contact someone immediately and dont drink the water.
It depends on the test you're using, but chloramine (chlorine+ammonia) in your tap water could be detectable with the API ammonia/ammonium test. It is detectable in mine, but the ammonia is readily converted by bacteria in the tank.