SeachemReef Complete Liquid ionic Calcium Source, 500 ml

I have an activated carbon reactor, will the reactor remove this stuff?

What distinguishes this from their regular calcium additive?

Seachem reef calcium. will it help strengthen the shell of my freshwater turtle? i have a reeve’s turtle/chinese pond turtle.

My calcium (159) and magnesium (870) levels are low in my nano 13.5g saltwater tank. Will this boost both or do I also need a magnesium additive?