Aquascape AquaBlox Water Storage Module Block System for Pondless, Waterfall, Water Features and Garden Drainage, Small | 29491 Modular water storage system ideal for use with Pondless Waterfalls, RainXchange, and other applications Holds approximately 7.4 gallons of water per cubic foot -- over 3 times the water storage capacity of gravel Load-bearing top supports up to 5,472 pounds per square foot Fast installation; requires less labor and uses less liner; comes complete with four structural supports Small size measures 26.5 x 16 x 9.5 inches (LxWxH) and has a 17 gallon volume