Here is a small step-by-step guide on how to properly buffer expanded clay. Expanded clay is a very popular and excellent planting medium. Expanded clay is chemically neutral, stable in structure and provides excellent drainage and aeration for the roots. The ph value of expanded clay (hydrocorrel) is naturally around 8, so it needs to be adjusted so that it is ideally around 5.5 to 6.
This is how expanded clay is buffered:
Pour fresh water into a large tub and check the pH of the water with a pH meter.
Lower the pH value of the water to 5. To do this, add a few drops of pH Down to the water, stir, wait 10 minutes and measure again.
If the water has a pH value of 5, pour the expanded clay into the tub and stir well for several minutes. Then leave the expanded clay in the water for 24 hours.
After 24 hours, measure the pH value. It will normally have risen to 7 again. Therefore, take the expanded clay out of the tub with a sieve, renew the water and adjust it to pH 5 again, stir in the expanded clay again and let it stand for another 24 hours. Now measure the pH value again, it should now be 6. You can now sieve the expanded clay and use it as a plant substrate.
When changing the water, you will notice that clay sludge has settled in the tub. If this were to remain on the expanded clay, it could cause problems with filters and pumps in recirculating systems.
Reuse Hydro Correls
Hydro Correls can be used over and over again. After one pass, they should first be soaked in chlorine bleach 5%, Enviro Clean or similar (approx. 24 hours) and disinfected in this way. Then rinse well and buffer with ph-corrected water + enzymes (e.g. Pure Enzyme from Plagron) as described above. This eliminates germs and pathogens and prevents them from spreading further. Then the new cycle can start.
