Eco-blox are used underground to create underground water storage reservoirs. It holds more water in a smaller volume reducing the size of the basin. Eco-blox easily lock together for a secure and extremely strong fit. They are strong enough to support landscaping, stone, gravel, etc. placed above them. They can easily be organized in many different ways and levels to work with practically any basin. Each eco-blox holds 31 ½ gallons of water, making them perfect for your pond-free water features, fountains or rain harvesting projects.