[64Ivy]

I know a service tech who's been using tap water for decades. Granted, he doesn't maintain much in the way of "SPS", mostly just fish short term for customers, but he does keep a 40g tank of his own and uses tap water for that one too. I don't know what his tds is but I live the next town over and mine is around 311ppm. Bottom line is that he doesn't seem to have any more casualties than most of us so I guess it's working for him. Nevertheless, after seeing what my RO/DI pulls out, I wouldn't be without one.