even on a well i've always use conditioner.. if not for chrorine the heavy metals we have in our wells here. not sure how it goes over there.. but here it's pretty easy to get a diagnostics done on your well, and the sewage plants should have water quality numbers for you. otherwise full work up kits aren't expensive ( iir here they are 20$, they test for just about everything. we had elevated levels or arsenic in our water. I wouldn't drink it even after it went threw a system.. and i surely wasn't going to expose my fish to it.) imo the greater danger are heavy metals in water not neccisarily chlorine. I look at it this way.. if i wouldn't even drink it.. i wouldn't expect my fish to live in it.