Couldn't find anything in the Vancouver retail stores. But I now you use this stuff. Have done a couple water changes with it now, and my tank and corals all look fine. It raised the Mg as expected.
http://www.canreef.com/vbulletin/sho...369#post861369
I mix it 10:1 with Epsom Salts. Here is a good article.
http://reefkeeping.com/issues/2006-07/rhf/index.php