I'm sorry, I can't remember, are you doing FOWLR
or reef. If FOWLR
, I don't think you would really need to worry about Ca
, regular PWC
should replenish all your depleted elements. I bought that kit and used it twice, once to see what my tank had and once on my well water, and I can't even remeber the results.
As for reef, I am not too sure. I have seen folks use "purple up" (I think) for coraline growth. I try to stay away from adding chemicals to my tank and let nature run with it. That coraline should grow under good water conditions.