Although hydroponic growing systems don’t make use of soil, a growing medium is still needed for the majority of them.
Ideally, this needs to be something that will store and deliver just the right amount of nutrients and moisture to your plants, which is exactly why expanded clay pebbles are such a popular choice.
What are Expanded Clay Pebbles?
Expanded clay pebbles look like small, marble-sized balls of clay, although they are slightly oddly-shaped and just semi-rounded, rather than being perfect spheres.
They are produced in a rotary kiln – pure clay is heated up to temperatures over 2000°F, which separates it into small pebbly units while filling each one with tiny air bubbles. It’s those very bubbles that make clay pebbles such a useful growing medium, as each air pocket is capable of holding moisture, nutrients, and oxygen.
Clay pebbles are known by a few different names, such as:
- Leca balls (which stands for light expanded clay aggregate)
- Hydroton clay pebbles
- Clay balls
Pros and Cons of Leca Ball (Hydroton)
Pros:
- Clay pebbles are great for retaining moisture and nutrients, but they also encourage drainage of excess water, preventing roots from becoming over-saturated.
- The air bubbles within each pebble, along with the space that surrounds them in their growing container, allows for plenty of oxygen to reach plant roots.
- Leca balls are sterile, meaning that you won’t need to worry about your hydroponic system becoming contaminated/infested with pests or diseases.
- The pebbles retain their pellet-like shape throughout the entire growing process, making it easy to remove both seedlings and older plants from their growing containers whenever you need to.
- Clay pebbles are pH neutral, so won’t interfere with the pH of your nutrient solution or plants.
- It is easy to reuse clay pebbles – simply give them a wash to sterilize them and then place them into a new growing container.
- Clay pebbles are inexpensive if you have a small-scale hydroponic setup.
- Clay is a natural material, making clay pebbles a renewable growing medium.
Cons:
- Once saturated, clay pebbles can end up quite heavy, making them unsuitable for large systems where growing containers need to be moved.
- Although they can be reused, washing clay pebbles will leave you with lots of red dust, which can end up quite messy. If you don’t wash them properly, that same dust could end up clogging your hydroponic system.
- While clay pebbles may be natural and renewable, the clay used to produce these is strip-mined, which is not very good for the environment.
- Pebbles that haven’t been fully saturated before use, or those that have dried up during the growing process, can end up floating, which could cause blockages in your hydroponic system.
- The excellent drainage qualities of clay pebbles can mean that the growing environment is too dry for certain plants, unless your hydroponic system allows for a continuous stream of water. If not, you may need to mix clay pebbles with another growing medium.
- Clay pebbles can end up quite costly compared to other growing mediums if you have a large-scale hydroponic system.
Let’s watch this video:
How to Use Clay Pebbles
Rinsing Clay Pebbles
Before you use clay pebbles in a hydroponic system, you will need to first wash them. This will clean them of the above-mentioned dust, as well as any other debris that settled on the pebbles during their manufacturing process, all of which will have otherwise clogged up your hydroponic system.
Simply rinse them in fresh, running water, until the water runs clean.
Soaking Clay Pebbles
Once you are certain that your clay pebbles are clean, you will need to soak them. The point of this is to fully saturate the pebbles and all of their micro-pores before they come into contact with your plants – this means that the roots of your plants won’t have to work quite as hard to find the moisture that they need.
You can either soak your clay pebbles in water or in a very diluted nutrient solution.
Either way, they will need to be soaked for a minimum of six to eight hours. If you are able to wait 24 hours, then that’s even better!
Once you lift the clay pebbles out from the water in which they were soaking, you will notice that they feel much heavier in weight – this is a sign that they are now well-saturated.
Using Clay Pebbles
Once your clay pebbles have been fully soaked, they are ready to be used in your hydroponic system.
Simply place them into your growing container, either on their own or mixed with another growing medium, before adding your plants in.
Using Clay Pebbles for Germination
Clay pebbles are great for both small and large plants, but you can also use them to germinate seeds too.
However, due to how good they are at draining away excess water, this can leave seeds too dry to germinate, so you would need to crush the pebbles first. This will increase their surface area, enabling them to retain more moisture.
To do this, first place your clay pebbles into a bag. Then, use a hammer to break up the pieces, until they have crushed down into much smaller particles. However, be careful not to crush them too much – if they turn into a powder, they will fall through the drainage holes of your growing container.
Once you’re done crushing the pebbles, place them into pots or trays, just as you would with any other growing medium, and sow your seeds. Don’t forget to soak the pebbles first!
If the humidity in your growing environment is particularly low, consider placing a humidity dome over your growing containers, as this will give your seeds a good start.
You will need to regularly mist your clay pebbles throughout the germination process. This can either be done manually, or with the use of automated misters.
Once your seedlings have developed a root system, you can then gently lift them out and move them into a container with full-sized clay pebbles.
Let’s take a look at this growing guide:
Using Clay Pebbles for Rooting Cuttings
Although clay pebbles are quite lightweight, they are steady and sturdy enough to hold even a delicate plant cutting in place. They provide just the right amount of water and nutrients while being completely sterile, which is why cuttings thrive when rooted in clay pebbles.
There are a couple of ways in which you can use clay pebbles for cloning plants:
1) Deep Water Culture (DWC) Systems
Also known as the low transplant technique, this method requires you to provide plenty of humidity to your growing environment.
You will need to fill your net pot about halfway with clay pebbles, but only insert your cuttings so that they are just an inch below the surface of the pebbles.
This way, the pebbles at the bottom of the pot will still be able to access the nutrient solution in your DWC system. They will act as a wick, providing your cuttings with enough moisture without the risk of drowning them.
2) Drip Systems
Also referred to as the top drip method, this technique involves rooting your cutting directly in its final location. The obvious benefit to this is that you won’t need to move your plant once it develops roots, which really preserves the integrity of the root system.
However, your cutting will probably need access to more drip emitters – aim for at least three per cutting, with each one releasing about a gallon of water each hour.
Make sure that your drip emitters have been inserted as close to the base of your cutting as possible, so that the nutrient solution is delivered directly to the part of your cutting that needs it the most.
Do check out our other hydroponic growing system guides: Wick System, Ebb and flow, Nutrient film technique
Hydroton/Leca Clay Growing Tips
Never Allow Your Clay Pebbles to Dry Out
No matter what you may be growing, one of the most important things to remember when using clay pebbles is that the pebbles should never be allowed to completely dry out.
Not only would this mean that your plants won’t have access to water, but the clay pebbles will end up absorbing moisture from the plants themselves, which would quickly be fatal.
Clay Pebbles Need to Be Rinsed Regularly
Although clay pebbles are known for being inert, they do still absorb nutrients, and some of these end up sticking around. Over time, certain nutrients can build up to toxic amounts, which will prevent your plants from absorbing the nutrients they actually need.
You often won’t be able to see this happening until the build-up has gotten quite severe, in which case you will notice a white residue forming over the top of the clay pebbles.
This is why you should be removing the clay pebbles from your hydroponic system every few weeks and giving them a good rinse, washing away any nutrients that may have taken hold. You will need to use fresh water that has a neutral pH, or a pH-neutral solution, to do this.
If you are in between crops, then you can save some time by just flushing out your entire system with a pH-neutral solution instead, rather than removing the pebbles.
Fully Sterilize Clay Pebbles Before Reusing Them
As mentioned earlier, clay pebbles can be reused, but they do need to be fully sterilized first.
Use other isopropyl alcohol or peroxide to do this, before allowing them to naturally dry.
Once dry, give them a long soak in your nutrient solution before adding them back into your hydroponic system.
Conclusion
Whether you’re starting seeds or growing mature and bushy plants, expanded clay pebbles are an excellent growing medium of choice.
The way in which hydroton clay pebbles retain water and nutrients while providing consistent aeration throughout the entire growing process makes them suitable for just about every type of hydroponic system out there, and the fact that you can reuse them multiple times is a huge bonus too!
Do check out our guide on other hydroponic growing medium too: Rockwool, Coco Coir
