One of the tricks I learned on this site for harsh water is to add some salt. I tried it last summer and the family noticed the difference immediately. You can search here to find the right amount. Go slow, adding a bit, swim a bit, add a bit more.... repeat as needed. We stopped just at the point that you could barely detect the taste.

As I recal I added about 4 bags of 40 lbs each to our 16 x 32 IG ( about 17,000 to 18,000 gallons )

Good luck