HYDROTON is a unique substrate for hydroponic gardening. HYDROTON is made from expanded clay in the form of round pebbles. Thanks to it's unique form, HYDROTON keeps an excellent oxygen to water ratio which provides the best environment for great root development, excellent nutrient intake and lowers the risk of diseases in plants. HYDROTON can be used as an indoor/outdoor main grow medium or mixed in with coco for better oxygen ratio and drainage. It is also recommended to place a layer of HYDROTON at the base of each pot (especially soil) to increase drainage.