.25 mm effective size sand (top 3 inches) – it took 80 lbs of this sand. Total sand weight: 680 pounds. Gravel weight 90 pounds. Water weight 240 pounds. Total weight 1010 pounds plus the plastic barrel – half a ton. As of Nov. 22 the .45 mm sand was made 4 inches deeper by removing the top layer, and adding more .45 mm sand. As of Dec. 14, a new top layer of .25mm sand (3 inches) 7.5 cm deep was added to cover the .45 mm sand, and the filter was restarted.