Be aware that nearly all dechlorinators, including Prime, do not remove ammonia but instead convert it to ammonium. Ammonium is detected by most test kits, including the API kit, as being the same as ammonia. Ammonium is not harmful to fish and also has the characteristic that it is processed by the autotrophic bacteria just as if it were ammonia.
Unlike chlorine, when chloramine is used by a municiple water system, the dechlorinator will break the ammonia and chlorine apart, leaving a trace of ammonium in the fresh tap water, which would then be detected by the test kit as a trace of ammonia of course.
There are a few ammonia test kits out there (Seachem makes one of them) that use a different method that distinguishes ammonium from ammonia but its important for beginners to realize that this is just another one of those areas where its better to learn to understand the *context* in which the test is performed. Its very rare to actually need the ammonium/ammonia separation tests for an action one would take.
~~waterdrop~~