anything you buy to decorate your tank or any gravel or sand  you should rinse it before you put it in the tank you must not ever put rock's from outside in the tank no matter if you rinse it off the rock will still have something on it from being outside that maybe harmful to your fish alway's buy the rock's & stones  from a petstore & rinse it off before you put it in your tank it's much safer& don't ever use soap or any cleaner's like bleach,  or any detergent cause it's harmful to fish  just rinse it off .