Hello; Well water can be tested. At some level there will be a place where you can get the well tested. Might be thru a state or federal agency or a private company but it can be tested to see if it is safe for consumption and/or safe for bathing. If found safe for consumption then I would use it for fish. Check with the county ag agency as that may be a place to get information.
My take is we pretty much all consume less than perfect water. I do not see how as much junk as we all put into the environment can help but to affect the water.