How To Prepare And Reuse Hydroponic Clay Pebbles. Here’s a little step-by-step guide to preparing my favorite growing medium clay pebbles also called expanded clay or hydroton. Expanded clay is a very popular and excellent planting medium. Expanded clay is chemically neutral, stable in structure and provides excellent drainage and aeration of the roots.
The ph value of the expanded clay is about 8, so it needs to be adjusted so that it is ideally 5.5 to 6.
How to buffer expanded Clay Pebbles:
Fill fresh water into a large bath and check the pH of the water with a pH meter.
Lower the pH of the water to 5. Add a few drops of pH down to the water, stir, wait 10 minutes and measure again.
If the water has a pH of 5, fill the expanded clay into the pan and stir well for several minutes. Then leave the expanded clay in the water for 24 hours.
After 24 hours, measure the pH. It will normally have risen to 7 again. Therefore, remove the expanded clay with a sieve from the tub, replace the water and return to pH 5, stir in the expanded clay and let stand again for 24 hours. Now measure the pH again, it should now be at 6. You can now sieve the expanded clay and use it as a plant substrate.
When changing the water you will notice that in the tub clay sludge has settled. If this were to remain on the expanded clay, this could lead to problems with filters and pumps in recirculating systems.
How To Reuse Hydroponic Clay Pebbles
Hydroponic clay pebbles can be used again and again. After giving them a quick clean with fresh water, they should first be cleaned in chlorine bleach 5%, or similar and soaked for about 24 hours this will disinfect the clay pebbles and should kill pests and pathogens.
Then rinse well and then buffer with ph-corrected water as described above. So germs and pathogens are eliminated and can not spread further. Using this method the pebbles can be used many times before they need replacing.