Join Date: Mar 2012
Location: Apple Valley, MN
I live in Apple Valley and have the same very hard water. Directly from the tap it has a KH of 18-19. The tap has 20 ppm CO2 in it, so it's pH is 7.4 if tested immediately, but if you let the water sit out for a day or so the pH is 8.2, which is what your aquarium will end up being if you take no measures to lower it, or if you don't inject CO2.
Aqua Soil lowers my KH such that on Sunday, right before a water change my KH is at 6. After a 50% change it's up to 12 and then lowers back to six 1 week later. As for pH, with CO2 injection it hovers between 6.8 and 7.0. So far this is working well for me.