Fascinating article by somebody who seems to know somebody that went with Horst and Kipper during their expeditions into Asian water chemistry that resulted in the Book _The Optimum Aquarium_ and the creation of the Dupla product line... which begat the ADA stuff.

Bottom line: Cryptwater has stuff in it, lots, that our tap-water doesn't, plus it has doesn't have stuff our tap-water has lots of. While the dissolved gases and minerals affect all Crypts, the water hardness issue only affects the true blackwater crypts, others will do fine in the liquid rock that comes out of many of our faucets.