Depends on your geographic location... some places have much harder or softer water depending on the material in the water table. Google "water hardness map" and you'll see what I mean.
Just how hard is your water? Have you tested it with a GH
kit? Once you know the numbers, it can be cut with RO
water, but you need to know numbers first, and what kind of livestock are you looking to keep. Some fish, like cichlids, love very hard water. IMO
, the only fish that truly need
softer water are discus.... others can adapt. If you live in a hard water area, what do you think your LFS