I've been using this road salt for 3 years:
http://www.canreef.com/vbulletin/sho...esium+chloride I'm able to buy it from a local hardware store called Amco Wholesale. They used to call it Absolute Zero Meltdown but now its called Safe Step Magnesium Chloride Ice Melter. Its sold in a 50lbs bag for about $30 and I've gone through close to two bags of it while mixing it with Magnesium Sulfate.