Carbonate and GH is not the same.
I have used SMS and Turface that remove KH but leave the GH alone. I assume the other clays will behave similarly, but an actual test run is the only way to know for sure.
I have coral sand and oyster shell grit in the filters of some tanks, and it is not enough to offset the removal of carbonates by the SMS.
Soaking in liquid rock might help. So much carbonates the material gets saturated. Cannot remove any more from the water. That eventually happened with some of the SMS that I kept adding baking soda to.
Safe T Sorb ordered!