Growers worldwide use clay pebbles because they’re clean, pH stable, pH neutral, and suitable for a variety of hydroponic systems. The increased levels of aeration, superior water drainage properties and accelerated nutrient uptake make clay pebbles the ideal grow media for RDWC, Flood & Drain and Wilma Systems. Clay pebbles are made by firing up pieces of clay in a kiln, which causes them to expand. They’re made for use as a base substrate, which you can mix with other media. They’re lightweight, porous, retain moisture, and improve the oxygenation levels in the root zone. It’s a sterile substrate, which keeps your plants hydrated and healthy.