All Expanded Clay is not the same Hydro Crunch Expanded Clay Pebbles are made with only the highest quality clay, producing a media that is uniform, stable and low in inherent E.C, meaning you get the best outcomes from your plants. Our special kiln-fired Expanded Clay Pebbles are lightweight aggregate that is super-heated and formed into pebbles 8 mm round in size. The ceramic shell and inner pore structure retains moisture and releases it back to your plant's roots as needed. Clay Pebbles will not compact, ensuring excellent aeration for the life of your plant. Hydro Crunch Horticultural Expanded Clay Pebbles are made from 100% natural clay. They are clean, pH stable and offer great aeration and drainage in hydroponics. Due to their unique structure and ability to cover a large surface area, they offer the ideal environment to foster beneficial bacterial growth around the root zone, leading to naturally healthier plants. The heavier the clay the LESS porous it becomes. Our clay is light and has lots of air inside for better results in the root zone. Hydroton is very dense, so while it does not float, it also does not hold the air. Our Expanded Clay Pebbles is not suitable for flood and drain systems as initially it can float, however if used in media mixes in pots it is by far the better performer.