If you don't rinse it (and, actually, even if you do), be sure you add it to an empty tank and then add the water by pumping it (slowly) onto a bowl or saucer sitting on the sand until you are above the sand. Then add your live rock structure and, finally, completely fill the tank. Nevertheless, be prepared for a 1 to 3 day dust storm if you don't rinse it. Good Luck.