Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
What else is in the GH booster you have? Almost always there is magnesium, and often potassium, sometimes other minerals, too.
If adding all of these are OK, and you can add enough GH booster to get the Ca where you want without over dosing the other materials, then go for it.
If you know that all you need is calcium, you might look for calcium chloride.