Hi, I finally picked up some new RO water from my local natural food store. Our city water is quite hard to begin with, but I was surprised at the results. This store has a very high end RO unit with UV as well. Results: TDS - 8, GH 2, KH 6, Ph 8.5 (surprised me). I will have to look back at my notes to see if their Ph has always been that high.
My own RKIN counter top unit tests today: TDS 18, GH 2, KH 1, Ph 7.
I use my own RO water on two tanks with cardinal tetras, Cory Catfish, gourami, shrimp, oto, celestial pearl danio, and goby. I use Salty Shrimp to raise KH on my RO water. All have been doing great.
From what I have read, keeping the KH steady at ideally at 4 is the most critical. Others here are quite expert, so maybe ask again! Hope this helps, please don't hesitate to ask more!
Fish+Plants thanks you!!