We found a combination water softener and filter like the SpotFree to be a very simple solution to hard dock water, which we encountered a few times in our travels and at the marina we used once we stopped cruising full time.
https://spotfreeh20.com/
There are a lot of these systems available, and they can be constructed DIY if you are minimally handy. One came with our boat and we were grateful to the PO for that.