I should add that people on RC and other threads say not to use anything that isn't Mag Flake, or made by dead sea works. They've done tests on the DSW stuff and it's good. They have not done tests on this, so i'm trusting the company that makes it to provide decent information.
Here';s the thread on boston reefers that gives all the stats of Dead Sea Works magflake:
http://www.bostonreefers.org/forums/...OR-NOV-MEETING