LECA : HYDROPONICS GROWING MEDIUM - Hydroponics .
L.E.C.A. (Lightweight Expanded Clay Aggregate) is made by heating clay under very high heat until it puffs up, like popcorn. This results in a very coarse medium; the balls are about 1/4" across. They have superb drainage and are sometimes added to denser media to help promote drainage in the planter. Lightweight Expanded Clay Aggregate