precisely what I am getting at. To achieve a single digit by changing water:
50% require 4 changes (50, 25, 12.5, 6.3)
30% require 7 changes (70, 49, 34.3, 24, 16.8, 11.8, 8.2)
20% require 11 changes (80, 64, 51.2, 41, 32.8, 26.2, 21, 16.8, 13.4, 10.7, 8.6)
changing water is a necessary evil. Of course, it has all the benefits. And frequent water change is definitely recommended. But From the calculation above, this will also make the salt sellers very happy.