Ammonia false positives?

[nirbhao]

I have city water, and sometimes it tests positive for ammonia. It's outright maddening to do a water change adding .5ppm ammonia, which I desperately hope is ammonium. It's not a false positive- it's that there's either ammonia or ammonium in the water. That's why the bottled water tests yellow.

 

[mikephelps79]

I've gone back to treating water that I'm adding with prime...just in case. Aquanova had need recommended by my lfs but it doesn't say anything about dealing with ammonia. Since the indicator doesn't go away during cycle, I'm pretty confident that something else is creating the positive.