It's a new way (but apparently and old way) to dose calcium instead of using a calcium reactor, and keeping dKH low, around the 6.5-7 mark. The basis is the idea that solutions made from calcium chloride and sodium bicarbonate may contain the relatively high concentrations of calcium and biocarbonate ions required for the supply of calcium carbonate in a reef. Basically you mix a certain mixture of regular ol' sea salt, with sodium chloride, yep that's right, good ol' cooking salt. The man who discussed this is Hans-Werner Balling, the product manager for the German company, Dr. Biener GmbH, who makes Tropic Marin products.