Red sea salt is formulated for RO water. That is the trick to getting high enough calcium levels out of your sea salt. The other brands typically give your TAP water a credit of 100-150 for your source water calcium level. If you use RO with IO you will know what I am taking about ,you have to add calcium. That is because IO is formulated for tap water. This is Red Seas big marketing point.
Since I do not use RO and My calcium levels in my tap water are high I precipitate enough calcium into my salt water Trash can as it is, so I have never thought to use Red Sea. Just more chalk dust to clean out of my trash can.
Scott