Hydrostone LECA Balls - 6 LitreHydrostone is more famously known as LECA that stands for Lightweight Expanded Clay Aggregate made by firing natural clay at high temperatures. At high temperatures the clay aggregates develop a honeycomb structure that can hold water and air the two most essential components for plant roots. This makes the hydrostone a perfect soil less plant growing medium. Excellent for use in indoor gardening to improve soil drainage or growing plants via