Digi-Lumen Extreme LED Controller Box clay pebbles and they are

clay pebbles and they are suspended above a tank filled with nutrient solution

5 mm    Material (Seed Tray)    PET Plastic    Cell Count    40    Total Vents    2 (4 with extender)    Product Manual

we still recommend the use of House & Garden HYDRO A/B

DE-Nat creates a barrier over the top of your medium/substrate that features abrasive properties and control unwanted visitors within your substrate

Digi-Lumen Extreme LED Controller Box clay pebbles and they areThe Digi Lumen Extreme Controller is a compact, easy to use digital LED lighting controller designed for precise control of up to 50 compatible fixtures. It features programmable ON OFF timers, a built in clock for accurate scheduling, and smooth dimming from 10% to 100%giving you complete control over your lighting environment. Multiple units can be daisy chained via dual RJ12 ports using standard 010V signals, with simple button controls, a clear