I even Googled this one, but found nothing to help. Today when I bough the girl's feed, I also asked for oyter shell. The people I trust most at the feed store told me they had coral. Please let me know if any of you have tried both and if you have a preference. Has anyone looked into the possibility of us contributing to the loss of coral reefs? I don't want any part of this unless it's harvested from DEAD reefs.