How to use pumice and bottom stones in Hydroponics

How to use pumice and bottom stones in Hydroponics

As a hydroponic grower, you will find pumice an ideal choice as grow medium due to its overwhelming advantages. Pumice stone is porous in nature and can hold the vital nutrients in its microscopic pores on the surface. You will find this of immense help in regulating fertilizer feedings. Since they are loosely packed in the bottom of the net pot, your hydroponic plants are assured of the much needed water and air circulation. Here we discuss how to use the pumice and bottom stones in your hydroponic grow pots.



After opening the pack, rinse and soak the pumice stones to remove any debris and dust collected on them. This process will help to provide a clean start and also avoid the murky problems in the reservoir. Soak for 6-24 hours before planting so as to let the water percolate through the stone’s micro pores. This will leave the media completely saturated.


Add little quantity of nutrients

After you rinse the media, place the stones in a container filling it with the nutrient solution you use for your plants. Maintain the EC at less than 0.4. If you do not have an EC or ppm meter, go by the rule to add the base grow nutrient at one-quarter strength. If you wish to ensure a smooth transition while transplanting, you can even use a hydroponic plant enzyme.


Two methods of laying

Hydroponic growers use pumice as growing medium in two ways – low transplant method and top drip method. If you choose the former, add the pumice stones to the net pots for about half and plant the stem at about 1 inch below the stones. In this method, the portion of the pumice stones submerged in the reservoir will work as a wick for the two or more inches above the water line where the plants are positioned. Drip systems employ the top drip method where the plants are placed directly in the grow medium and drip emitters are placed close to the plants ensuring a sufficient flow rate.


Rinse periodically

No hydroponic system is completely inert since most of them have a typical pH value and cat ion exchange capacity (CEC). You might often notice that the pumice or bottom stones invite a whitish substance deposit on top of them. This is the result of the salt residue left over by the nutrient solution. If you allow this to develop for too long, it can lead to phyto-toxicity that can choke out and starve the plants without nutrients. To avoid this, when you grow in pots, pull the plants out of the system and rinse the pumice stones using fresh water that is adjusted for pH. If not using pots, then rinse the entire system to clear off the toxic build up in the system.


What you must not do with pumice stones

  • Do not allow the pumice stones to dry out.
  • Do not use pumice stones in regular pots where there is no dedicated water source.
  • Do not introduce them in the system without sterilizing with isopropyl alcohol or peroxide.
  • Do not use pumice stones in lieu of soil while planting outdoors.


Recommended Products

  1. Pumice/Bottom Stone Click here to see pumice/bottom stone
  2. Medium Nutrient Soil Permeability and Drainage Run Stone Pot Bottom Click here to see this product

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  • Paul Barry
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