Been on wetwebmedia and seen a few post referring to calcium gluconate for coralline (attached one). Assuming the Anthony is Anthony Calfo.
Calcium supplement
What brand of calcium supplement would you recommend for live rock?
<for coralline growth only I really like Seachem's Reef Calcium (an organic sugar-based calcium gluconate). Simply outstanding for growing coralline algae (pink/purple, etc). 4 months of faithful use and it will look like a whole new tank
For coral growth however, kalkwasser supported by proper alkalinity (buffer) is recommended when a calcium reactor is not possible/present. I use a Knop calcium reactor from General Aquatics for convenience but still like kalkwasser very much. Best regards, Anthony>