Mother Earth Hydroton, 25-Liter Clay is mined, formed into pellets and fired at high temperatures to cause the clay to expand into lightweight balls Clay naturally has balanced capillary action to accelerate plant growth with an ideal surface for root structures and beneficial bacteria's Mother Earth Hydroton drains freely, is pH adjusted, free of harmful heavy metals and inert Each batch is tested before bagging to ensure highest quality For best use, rinse before planting