That is awful info from the water company! I would be using filtered water, or bottled or RO
water from a fish store and remineralize it.
Alternatively you could get a trash can or 5G buckets and run ammonia detoxifier /chemical media to get the water to start out with good water parameters with your tank!
The similar thing happened to me when I began keeping shrimp. Mine was only .25 ammonia but I did find out it was from the water, yuck!