kalk mixture

Here's another article about kalkwasser that I found helpful.
http://reefkeeping.com/issues/2005-01/rhf/index.php

Also, if you're thinking of adding kalk to topoff water, just keep in mind that your calcium/alkalinity consumption rates are not tied to your evaporation rates. I evaporate maybe 30-50% less in the summer than I do in the winter I'm guessing due to humidity levels in the summer in MN.
So that completely changes my dosing amounts if I only rely on kalk in the topoff. Of course this depends on your area and how your setup works but I just wanted to add that bit since I hadn't actually considered that when setting up my tank.