If you are using rock that you have used peviously in a freshwater system, make sure that you have not treated with a copper based med at any time with it. Lace rock can be found at almost all LFS or even at the landscape supply. You just will have to sift through it for a while. Your LFS will have the premium pieces at about a buck a pound. I set my tank up with 90 pounds of live rock and 80 pounds of lace base rock.