I also live in Wisconsin and have similar water quality. My water has a natural
KH of 16 degrees and a natural PH of 8.2. The best advice I could give you is what has already been said, don't worry about it.
However, if you are going to worry about it then you could try
CO2 injection. For under $5 you could build a DIY
CO2 system. I have one and my PH is down to 7.4. With a 55 gallon tank you will need atleast 2 2 liter bottles. Probably more. I don't know if you could or should try a DIY
CO2 system on a 100 gallon though. And while you're injecting
CO2, you might just want to think about getting live plants. They'll love the
CO2 and the hard water.