Well this is what i did, there is some difference in opinion though. I had Crushed coral for about 6 months, then i changed it over to Live sand. First i scooped out all my crushed coral in one day, like 1 hour, lol. let the tank settle about 24 hrs, then i added my Live sand. I had No spikes or really no changes at all with any of my water parameters. Best of luck to ya Todd