How to Use Hydroton (Expanded Clay Pellets) in the Garden ...
Expanded clay pellets (Hydroton) are made by heating the clay to over 2,000 degrees Fahrenheit. The process is done in a rotary kiln. As the balls heat up, they fill with bubbles and form into small marble-sized units. While the clay can be used on its own for growing plants, it can also be mixed with soil and other growing media.