I picked up a 50 pound bag of childrens play sand at Home Depot as suggessted by a number of members because it is so cheap and looks nice for 5 bucks. I am wondering if I have to remove the water from the tank before I add the sand in ? I plan on leaving the filter off for a few hours to let the sand settle before I turn it back on. Please let me know because I want to do this tonight. Thanks.