I found Caribsea Reef Rock which is fossilized coral does anyone have any experience with this. I think I'm gonna give this stuff a try its only $2/lb.
As long as it's dead, it's fine & will help add hardness to the water.
As far as adding LR to a SW tank--it must be completely cured (taken from a fellow reefer's tank is best) or you need to cure it a bucket before adding to any tank with livestock in it.