[Mark Allred]

We need to reconstitute my friend's softened tap water for her 75 gallon aquarium.
Bypassing the system is probably not an option. I know Gh can be reconstituted with CaSO4.
My concern here is raising the pH, her pH is already 8+. I believe the KH can simply be boosted with Sodium bicarbonate?
Any ideas are greatly appreciated!

 

[Hoppy]

I question adding more sodium to softened water, so adding sodium bicarbonate seems to be a bad idea. Using water from a water softener isn't a good idea anyway because of the high sodium content. If you use potassium chloride in the softener, that also tends not to work for a planted tank, for reasons that aren't clear to me. Perhaps a RO system is the only good solution for this situation.