Hydro Clay Pebbles Grow Medium - 5L 10L 25L & 50L Bags - Great Growing Media Used In Aquaponics and Hydroponics (10 Liters = 7.2 lbs) Pebbles porous structure provides excellent aeration and acts as a water reservoir Records high and low points for both temperature and humidity Made of 100% natural clay. Pebbles are of uniform, round shape. Inert, pH-neutral, and decorative. 8-16mm pebble size range Pebbles have thousands of tiny air cells with a hard shell of baked clay Primarily Used In Aquaponics and Hydroponics