Canna Aqua Clay Pebbles 20LCANNA Aqua Clay Pebbles are manufactured from special types of clay that have a low soluble salt content. Because of this, they are particularly suited for use in closed hydroponic cultivation systems. Advantages of CANNA Aqua Clay Pebbles CANNA Aqua Clay Pebbles have both high porosity and high air content which stimulate the development of strong roots that grip the substrate well. Strong roots mean bigger yields. Aqua Clay Pebbles are inorganic,