Magnesium Chloride source

[ReefTeacher]

So I am looking for a locally available MgCl2 source. Has anyone any info on the safety of

http://www.vitaminshoppe.com/p/life...flakes-44-oz-4-oz-flakes/ly-7111#.V31e74-cHD4

Is says 100% pure, but then it also says 1 cup contains 51 grams of Magnesium Chloride. That certainly isn't right even for the hexahydrate. Ideas?

 

[bertoni]

If you're in Boston, you might be able to find Mag Flake, which is sold as an ice melter, although now is a bad time to be looking. I personally wouldn't trust that product, but it might be okay. You could use magnesium sulfate until winter time.