If you are getting swings, the way to solve it is to get the water to the setting you want, then add 2 tsp per gallon of kalk to your ATO reservoir. That doses it constantly, or at least adds very little, and keeps your calcium level and alk steady. You need a magnesium level of 1350, calcium at 420, alk at 8.3, and with kalk (Mrs Wages' Pickling Lime), it will hold very steady.