We also had well water growing up, never a problem. I'd had friends over the years, either buy distilled water to fill their tanks (of course they were smaller than yours) or fill their tubs, buckets whatever with tap water and let it sit for a day or so. They said it worked, no dead fish lol. I think it's because most city tap water comes from a municipal water supply that is chlorinated. I live in the city, and i fill an old water jug with tap water let it sit for couple days to water my house plants, especially violets.