Kurt is right on.
You want to keep calcium between 380-450 ppm
(having it higher does no good or no harm...to a point), alk
between 7-11 dKH
(both higher or lower can cause problems) and mag around 1300 ppm
. Also, keep in mind that phosphate inhibits calcification, so if you have high phosphates it can/will prevent corals/coralline from growing. It all works hand in hand.
Here's the link to the RC Chemistry archives. You can find just about anything you may want to know there.
Reef Central Online Community Archives - Reef Chemistry Articles