I have a 90g reef tank. It's mostly live rock and soft corals, with a cleaning crew of stars, crabs, snails, etc., and 3 fish. Have been using crushed coral for the past few years, but since I am moving and will toss out all of the old substrate I am pondering making the move to sand. Any advice on that decision would be appreciated. Also, how many pounds of sand should I use? Like I said, it's a 90g tank with probably about +/- 90 pounds of live rock. Thanks.