Although I don't take Coral Calcium, I do have to put what I know about it.
For one, the ONLY Coral you should get is from above sea and any lead or mercury is WAY below what the government deems unsafe. For more info: http://www.coralcalcium-watchdog.com/
Just do what you feel is right, I know on some MD websites there are cancer patients who were taking Coral Calcium and their overall health improved and the tumors were reacting better to chemo and the doctors were in disbelief.
If you want to see those testimonies, do a Google search.