Try this article out, it should answer everything:
The “How To” Guide to Reef Aquarium Chemistry for Beginners,
Part 2: What Chemicals Must be Supplemented
http://www.reefkeeping.com/issues/2007-04/rhf/index.php
Everyones tank is different. With my main one I run both a calcium reactor and a kalkwasser reactor, I boost my IO salt with a magnesium chloride/sulfate mix and I drip a little lugols iodine every once and a while.
With my nano I just do water changes. Period.