Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Get some RO water from the grocery store and test mixes with your tap water. Test GH, KH and pH. Really try to get the GH and KH right, and not worry so much about the pH.
25% Tap + 75% RO
75% Tap + 25% RO.
Run the test for a week or two, testing every few days, to be sure the mix is stable.
If you like the results then you can buy the RO from a grocery store or fish store (shop around for price) or you can buy a reverse osmosis filter for your house. There are some that sit on the shelf and might produce enough for a water change, but are pretty slow. If hard water is also a problem in the house (soap won't lather...) then you might look into a whole house filter that works in stages.
do small frequent water changes to introduce the new water to the livestock. Perhaps 2-3 25% water changes per week for a month will lower the mineral levels slowly enough that the fish and shrimp will adapt.
After that you can do whatever water changes are needed, but will need to mix the same recipe every time.
Top off with reverse osmosis water.
The same info will work if rain water is a viable option for you.