If you can add live plants, anything will be better then non, most ideal new set up is 0% plant cover in the tank (not only for your water, but mainly to be natural for your fish). You can gladly look at my tanks here on the left tap that say's "Aquarium"
AmQuel detoxifies ammonia and transforms it in to a NON toxic ammonium for fish. You WILL still get the ammonia reading on your test kit but the water itself is safe for fish! So that's a BIG plus knowing you're using it!!!!
You may as well test your tap water
, poor a cup at night, let it sit and test it in the AM. A lot locations around the US have ammonia in their tap water. If that's the case with you, then with each water exchange you detoxify it but you would then always get readings. So check up on that end too!
Bottled water is RO (reversed osmosis) water and thou its a clear liquid looking like water, it has zero minerals in it compared to your tap, so its not really helpful but (unless used in excess) also not harmful to my knowledge. And I donno what size tank you have there, but with all these water changes that's been long out of the tank's system
So test your tap and do not give up!!!!