So can you test your tap water and see if there is ammonia in it?
If not or say .25, removing the water from the tank in the danger zone is perhaps more
easily done than adding tablets, and there is other danger that the water has NitrItes in it and could also have NitrAtes, can be injurous to the fish.
What is it that you use to make your well water safe to drink? Does it go through a UV treatment or have something else?
If you have a safe unchemical or chlorinated treatment, change the water as soon as you can.
Issues with well water, I only am familiar with a few, are heavy metals in the ground which can be found from natural mineral sources, or from contamination.
Well water treatment used is water softener, removal of minerals calcium and magnesium, which help fish with osmoregulation in their bodys, addition of salt, not helpful for fish to thrive, not having the other necessary minerals.
https://www.cdc.gov/healthywater/drinking/private/wells/treatment.html