From the Reef Aquarium Supplements Article:

Exactly which aquarium supplements to use is a complicated question. However, all reef aquariums will need calcium, an alkalinity buffer supplement and a trace element supplement. Instead of calcium and an alkalinity buffer you can use kalkwasswer.

• Buffer is used to maintain PH/KH. We recommend the Seachem Reef Builder or Balling Light KH Carbonate Mix.
• It is necessary to add calcium to reef aquariums in order to replenish the calcium utilized in the growth of soft and stony corals, pink coralline algae, calcareous algae, tridacna clams, and other invertebrates found in captive marine systems. We recommend using Seachem Reef Advantage Calcium or Balling Light Calcium Mix. You can use kalkwasser instead of calcium and buffer. Kalkwasser needs to be introduced into the aquarium slowly using a kalkwasser stirrer or reactor. Kalkwasser will provide both the calcium and the alkalinity. For more information on using kalkwasser please read the Kalkwasser Overview Article.
• You can use several types of supplements or just use a comprehensive formula to provide trace elements. With Fauna Marin Balling Light Trace 1 and Trace 2, you can mix trace elements into your calcium and buffer to dose them at the same time as your major elements If you would rather purchase a calcium and alkalinity supplement with trace elements already mixed in consider ESV B-Ionic.

... Reef Aquarium Supplements Article Continued