I used crushed coral for the substrate in my 55g SW
tank. It literally took me 5-6 hours to wash that crap. Wash until the water is clear and not milky white. I used my wife's strainer and a big older bowl. put it in there and kept running water on it and kept stirring it up. Once it was kind of clear i put it thru the strainer and rinsed again. If I were to do it again, I wouldn't go with crushed coral, I would have used sand.