Are crushed corals a viable source of calcium?

[Progen]

I have some deformed young leaves on my anubiases which according to some charts say is due to calcium deficiencies. I didn't use to have this issue when I had two bags of crushed corals in the tank which I later removed since I suspected that it was buffering the pH too much and making the drop checker unreliable.

Is the calcium carbonate from crushed corals usable by plants or must it be calcium sulfate?

 

[Easternlethal]

I would not use coral because it takes time to dissolve and you will have no idea how much calcium really is in your system and it will be tough to get rid of especially if you want to grow soft water plants later.