That's what I use and it is really IMO the best. I have a 50lb. bag I can get rid of BTW, but I am not sure what the forum protocol is on that.
Thought I would add a little from the package:
Media:
Calcium = 381,000 ppm
Carbonate = 590,000 ppm
Strontium = 7390 ppm
Magnesium = 1050 ppm
Potassium = 56 ppm
Hard Coral:
Calcium = 365,900 ppm
Carbonate = 590,000 ppm
Strontium = 6550 ppm
Magnesium = 791 ppm
Potassium = 50 ppm
So I am not sure exactly how that is possible since it appears to be made of coral bones, but it would explain why I never have an issue with magnesium.