I would be worried on initial discovery of this same as you probably do but technically speaking if you are using quality dechlorinater such as Prime or similar, and dose the relevant amount as per what your water report ammonia level is, you should be completely safe. I'd go the extra step of getting that report in order to know how much dechlorinator to dose...Other than that your filter bacteria would also be used to cope with your water regime and water quality, extra chloramines/ammonia and such.
I know not many can accommodate it, but emersed plants if you have an open top tank, or any gaps in the cover where you can stick in some plants(only their roots) that do get enough light, such as photos , peace lillies, parlour palm, and tens of others would mop that ammonia in a bit.
Also, the toxicity of ammonia is pretty much dependent on the Ph of the water. The lower the Ph, the more of the ammonia is in a pretty much non-toxic ammonium form, also dependent on temperature, same applies to it. You can research a bit and find the exact equilibrium between ammonia/ammonium ph and temperature...lots of info out there....and in fact a level of 0.50ppm in most tanks, unless really hard water, is not much to worry about taking all factors into account....The home liquid test kits test for total ammonia and can't distinguish between NH3(ammonai) and NH4(ammonium), the latter being non-toxic to fish. Also, dechlorinators can skew the result too...
If your fish are behaving fine and you're having generally pleasant and uneventful fish keeping experience, you've been doing just fine with what you've been doing. If not, there's plenty of advise here, change what you think you should change based on that and see how it goes from there..
All the best.
