No harmful chemicals for humans, I am sure. Fish and other reef critters, I must say, are completely different. There is a chance that what happened to your tank can be attributed in part to using tap water, especially considering the pH of well water is usually on the low side.
Considering the price of a bucket of RO water every two weeks or so and the price of some of the livestock you intend to be keeping... I see no good reason to continue using well water.
Mike