Plaster of paris - Calcium sulfate- this would raise the hardness of the water without affecting pH.
quartz - Inert AFAIK
. Maybe the crystals help channel positive energy into the fishies?
perlite - This is the white stuff you find in potting soil mixes. Also inert, AFAIK
methylene blue - People put this in breeder tanks to protect fish eggs from fungus. It's the active ingredient in BettaMax. I've also seen it used by people who transport fish to/from fish shows. I'm not sure what effect long term exposure would have on fish.
Bottom line: Interesting product, but I think frequent water changes are the best way to "maintain proper pH balance, better fish health, better resistance to disease and clearer water".