Hydroton Clay Pebbles: Expanded LECA Growing Balls

Hydroton is sometimes referred to as grow rocks, but this couldn’t be further from the truth. This growing medium has exploded in popularity in the United States, not only among hydroponics enthusiasts, but soil gardening as well. 

It’s been a popular growing medium in Europe for decades. But what is hydroton, and why is this peanut-sized aggregate so useful?

Cactus growing in Hydroton clay pebbles

What Is Hydroton – Clay Pebbles?

Hydroton is a highly versatile clay substrate, sometimes referred to as clay pebbles or LECA (lightweight expanded clay aggregate). 

They’re suitable for both aquaponic and hydroponic systems and their size and composition make them easy to handle and transport.

Also known as clay balls, expanded clay pebbles, and leca balls, hydroton is made of clay that has been heated to 2,000° degrees Fahrenheit in a rotary kiln. The result is a small, round pebble filled with air bubbles.

What Are the Pros and Cons of Hydroton – LECA Balls?

No substrate is perfect, but hydroton comes pretty close. Depending on your personal needs, they make an excellent alternative to rockwool, growstones, perlite, or coco coir. Understanding the pros and cons of this material are essential to successful growing.

The Pros

Environmentally-Friendly – Hydroton is a completely natural product which relies far less on clay than its nicknames suggest. As a result, it creates far less strain on the environment than other strip mined clay products such as cat litter. 

Even more importantly is that simply rinsing the clay pebbles can remove any silt or other debris and reused indefinitely. Thus they won’t clog landfills or significantly contribute to strip mining over time.

Large and Highly Porous – The larger size of hydroton pebbles allows for greater percolation than perlite, although its air holding capacity (AHC) isn’t as high. 

The size and shape means hydroton is more resistant to blockages, even when covered in biofilm or some debris gets caught between the pebbles. This makes hydroton clay pebbles perfect for aquaponic media bed and ebb & flow systems.

Its AHC level provides good aeration, reducing the risk of anaerobic zones, while the pores are able to hold a decent amount of water without storing too much.

Plant-Friendly – Hydroton is baked in large rolling kilns at high temperatures. As a result, it’s both sterile and pH-neutral. 

Paired with its ability to provide aeration even in soil planting, these qualities create a much safer planting environment. It will also store any nutrient solution or other liquid fertilizer you use.

Easy to Work With – The larger size of hydroton means this remains a loose medium. It holds its shape, so transport is easy. Harvesting plants or accessing roots for division requires far less effort, regardless of the growing system used.

Excellent Microbial Support – While the surface structure of these natural clay pellets feels relatively smooth, there’s enough biological surface area (BSA) to create a welcome habitat for microbes that break down organic matter to create nutrients which help serve as plant food.

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The Cons

Price – While relatively inexpensive for small growers, the cost quickly adds up, making them a hefty investment for large growers. 

This downside is offset over time, but the original hydroton cost may be prohibitive for some.

Cleaning – While necessary between uses, the cleaning process is time-consuming and results in a lot of reddish dust. Unfortunately, neglecting to properly rinse and soak the pebbles may result in this dust clogging the mechanical parts of hydro growing systems. 

Failure to adequately soak the pebbles, especially when using for the first time, may result in them floating and clogging filters or drain lines.

Water Retention – While they have a decent ability to retain water, the lower water holding capacity (WHC) means that they can dry out rather quickly if there’s inadequate watering. 

Hydroponic, aquaponic, and irrigation systems all bypass this negative aspect. However, this may be a problem for soil plants that require a combination of moist and well-drained soil.

How Is Hydroton – Expanded LECA Pebbles Used?

Hydroton is used in a wide range of gardening methods, with slightly different methods applied between hydroponic/aquaponic and soil gardening. In both cases, the clay pebbles should be rinsed thoroughly before the first use to get rid of dust.

NOTE: I grew Phalanopsis and Cattleya orchids back in the early 1970’s using Hydroton (LECA).

Hydro Farming

Hydroton is excellent for use with dutch buckets, deep water culture, drip, and ebb & flow systems. When using for any form of water-based farming, hydroton pebbles should be soaked for 6 to 24 hours. 

This allows the water to soak in and push trapped air out. Failing to properly soak the pebbles will result in them floating and possibly clogging vital systems. 

Soil Farming

You can crush hydroton pebbles to create a higher saturation level to create a good starting medium for seeds. Alternatively, you can place the seeds in net pots and cover them with a few presoaked clay pebbles. 

Manually spray the pebbles or use misters with a burst setting of 4 to 10 seconds every 2 to 3 hours for easy germination.

Avoid using hydroton in large pots unless it has a dedicated water source to reduce the risk of algae or drying out. They can be used in conjunction with soil in outdoor settings, but cannot support plant life on their own in a soil garden setting. 

A good ratio is 30% percent hydroton added to your chosen growing medium. A 1” inch layer at the bottom of containers further aids in drainage.

General Tips

Between uses, be sure to thoroughly rinse the hydroton. Soak them and sterilize with some peroxide or isopropyl alcohol to avoid the risk of cross contamination. Also, be sure to check the pebbles for any whitish residue. 

This is a sign that phytotoxicity has built up from frequent nutrient absorption. When this occurs, be sure to rinse both the plant and pebbles in a pH-adjusted liquid to restore proper balance.

Are There Any Special Fertilizers To Use With Hydroton?

Hydroton will work with your regular fertilizers in both hydroponic and soil gardens. A useful trick is to add a small amount of your preferred base growth nutrients to the pebbles at ¼ strength before placing them in the growing area.

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