when filling a large tank with water with a sand base, ..take a large black trash bag, ..and lay across the top of the sand. Place empty glass cups along the outer area and corners of the tank, ..Fill those cups with your water, ..then fill the tanks half way, ( unless you are placing base rock ect before adding water.) Then dump and remove cups of water, and wait a few seconds, the bag will float to the top, grab and remove. it eliminates most of your sand cloud.