Plagron - Euro Pebbles

Clay pebbles of 8 to 16 mm, baked in an open kiln into their irregular shape. Meant for hydroponic growing and for recirculating systems, and reusable for years.

They come out of the bag alkaline, and that sets your first rinse

Clay pebbles are sold as a neutral medium, and where nutrition is concerned that holds: they release nothing themselves, so you steer the EC entirely. But neutral here does not mean the pH is neutral. Plagron publish a pH of 6,8 to 8,3 for Euro Pebbles. That is alkaline, and distinctly so at the top end.

So that first rinse is not a cleaning job, it is a pH job. Plenty of growers rinse off only the clay dust shaken loose in transit, put the pebbles into the system, and watch their pH creep up over the first few days without seeing why. Soak the pebbles in water you have already brought to the right pH, leave them, then measure again. If the value keeps drifting, rinse once more.

Nor are they quite at zero for conductivity. Exactly how far off is hard to say: Plagron give two different values on their Dutch and English pages, so we print neither. Rinse until your own meter settles, which is more reliable than any figure on a bag.

Why recirculating systems in particular

The pebbles are hard and hold their shape. They do not silt up and they release no organic matter to block lines or drippers, which is precisely the difference from a medium that slowly breaks down. In a system where the same solution goes round and round, that is the property that counts.

After harvest you pick out the root debris and rinse them through. They last for years.

Available sizes

Technical Specifications:

• Type: inert hydroponic substrate
• Composition: baked clay pebbles, pure salt-free clay
• Grain size: 8 to 16 mm
• pH: 6,8 to 8,3 (EN13037, in water)
• Shape: irregular, baked in an open kiln
• Use: hydroponic growing, recirculating systems, drainage layer in the base of a pot
• Reuse: practically unlimited, after removing plant debris and rinsing thoroughly

Frequently asked questions

Why does my pH rise after I put the pebbles in?
Because they start out alkaline. Soak them in water at the right pH before use and measure again, rather than only rinsing the clay dust off.

Can I mix them through soil as well?
Yes. In the base of the pot as a drainage layer, or through the mix for more air. You are then using them to change the structure, not as a growing medium.

How often can I reuse them?
They barely wear. The practical limit is how clean you can get them between two crops, not the material itself.

Can I overwater on clay pebbles?
Not easily, because there is a lot of air between the pebbles. The likelier risk is watering too little, since they hold almost no moisture themselves.