I'm just East of the Twin Cities, in the beautiful St. Croix River Valley area which is nestled in limestone bluffs.
We are on city water, and they mail us the water test every year. I noticed we had no metals therefore I no longer use Metal Gon with each fill.
We do, however, have many minerals like you will, and I have been told that I MUST add Defender on a regular basis or things will clog up over time.
I did notice that they switched the directions on the bottle from one ounce a week to 2 ounces every other week. Weird. Does that matter at all? :-/ I like the idea of adding an ounce a week, that way, when I forget, it hasn't been as long before more is added!