Or from area to area? I'm glad I don't have to keep fish in London water!
I'm very lucky with the water where I am, it's lovely
Does cost a lot though
I think it also depends on what fish we're talking about. I wouldn't risk fry, wild caught fish or anything delicate with any amount of chlorine.
My big oscar, however, sometimes gets a scrape on his head or a lost scale ('cos he throws his decor around when he's in a strop, which is most of the time
) and I'll do a 50% change with chlorinated water to make sure no secondary infections pop up. I do keep the filters off and add dechlor before I switch them on again, just in case, but I'll leave it for two or three hours.
Dechlor is so cheap, most of the time there's no good reason not to use it though; I always dechlor each bucket for my emerald rasboras.
