I used the same method for years. Works like a charm. If you can find calcium chloride (I might Even have some you can have) you can dose calcium the same way. This is called 2 part dosing. Dan's recipe is nice in that it buffers the pH, where using the components on their own can cause small pH swings up or down, depending on how much you use. I eventually gave up on two part and just started putting kalkwasser (pickling lime) into my ATO water bucket because I'm so busy I was never able to added the 2 part reliably on a daily basis.
This is a helpful tool for figuring out the amounts of each component you need for two part dosing:
http://reef.diesyst.com/chemcalc/chemcalc.html