What are Hydroton Expanded Clay Pebbles, and How Do They Compare to Other Growing Media

The world of indoor gardening can be a bit intimidating to someone new to the world. Even selecting your growing medium can seem a bit too much. So what is the right one for your particular garden?

Before you look any further, look at this guide for information on hydroton expanded clay pebbles. It is one of the most popular growing media for hydroponic and aquaponics systems. 

What is clay, and how do they compare to other types of growing media? In this article, you'll learn what they are, their benefits and downsides, and how to use them. 

We will also explore some alternatives to hydroton pebbles you may want to consider if you're looking for something different!

What are clay pebbles?

Hydroton, otherwise known as lightweight expanded clay aggregate (LECA), hydroton, or clay pebbles, are clay balls that have been expanded to form clay pebbles. They are light, porous, and easy for transplanting and harvesting, making them an excellent choice for hydroponic gardening.

The clay balls and other minerals are heated to 2,000 degrees Fahrenheit using a rotary kiln until they expand and become a rock filled with air bubbles.

What are clay pebbles used for?

clay in hydroponic system

Clay provides a healthy medium that is resistant to compaction, which allows for better airflow than other mediums like soil or sand. In addition, it has tiny pores on its surface that help hold onto nutrients until they can be absorbed by roots nearby. 

The clay pebbles then become nutrient stores themselves over time as they continue to absorb rainwater and decomposing organic matter from leaves falling off into them. 

They also help maintain an even hydroton clay temperature throughout the year, which is ideal for root growth will maintaining neutral PH levels.

Clay is used in hydroponics. Its particles are saturated with water and nutrients. This increases the availability of both oxygen in this environment for root growth and also access to plant-available nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), sulfur(S) phosphorus(P).

Just be aware that clay pebbles are not ideal for all plants, and different types of clay will need to be used.

Larger ones with holes drilled through them allow the plant roots to grow out while keeping their head submerged underwater, so they don't dry out or get exposed to air. 

Smaller clay particles have more surface area on their exterior, which allows a more significant amount of nutrient solution uptake into the root system.

How do you use clay balls on plants?

Expanded clay pellets work best on clay-loving edible plants, like dry beans or parsley but not so great in combination with flowering plants like tomatoes because hydroton clay has nutrients it needs too, and it doesn't allow all the water to drain out (which is essential).

Sometimes, pebbles can be used in containers combined with hydroponics systems, and hydroton has been shown to provide better drainage. The water is not sitting there longer but instead draining out more quickly.

When using hydroton clay, you must use good quality, not containing heavy metals like arsenic (a known carcinogen). Those toxins will leach into the soil over time when exposed to moisture and cause your plant harm - even if only occasionally!

How to use them? 

Easy - don't work hard! 

Place the pebbles on top of your pots to create a small raised bed. You use them in conjunction with soil and not as a replacement, unless having a dedicated water source.

Some people say they can wash clay balls by hand or scrub them down with something abrasive before using them for at least six hours. 

Rinsing is especially true when using aquaponic systems, as hydroton clay out of the bag covered in red clay dust. This will prevent more expensive problems and save headaches.

In contrast, others prefer not to risk contaminating their roots with any leftover bits of dirt or chemicals. 

Expanded clay is very absorbent, so it might be best to go with a lighter soil mix that drains well. For example, like some type of coir (coconut fiber), that is not too heavy where the hydroton clay doesn't have time to drain out!

You could put them at the bottom of the pot if you're unsure how they'll do mixed in the soil. Then, you just take out any leftover clay balls when repotting later down the line for more space for new growing mediums.

Don't use a regular pot unless you have a dedicated water source. Using regular pots can sometimes lead to algae and draining issues. 

Can you start seeds in expanded clay pellets? 

transplant seeds in clay

Yes, expanded clay pellets make an excellent surface for starting seeds. Many people report that clay doesn't dry out as quickly or lose heat. What makes them perfect if you want to start your seedlings earlier without risking damage from the cold weather.

You can also transplant or seed directly into clay pellets when planting starts in earnest and not worry about disturbing their roots system later on.

Some growers prefer to crush the pebbles to increase saturation. In contrast, others like to sow seeds directly on top of a couple of intact and whole pebbles. Use small net pots, and cover the seeds with a couple of pebbles.

Misters set to bursts lasting for four - 10 seconds every two or three hours is your best friend when it comes to germinating impatiens. Just make sure you soak the pebbles beforehand. If you do not have misters, manual feeding will work as well, as long as you do not let pebbles dry out.

What do I need to consider if choosing clay?

Clay has many benefits but does have some downsides that should be considered too.

Expanded clay pellets desperately crave continual watering for the roots system to access oxygen from the air surrounding the growing medium. It uses its air bubbles to make sure hydroton clay doesn't dry out or decompose quickly.

Clay also compacts more than other mediums, so you need to make sure there is enough space for the hydroton clay to expand. Otherwise, they can't be watered and won't grow your garden well due to a lack of oxygen.

If you use expanded clay pellets in hydroponics, make sure your system has an aeration pump or something else that pumps extra oxygen into the mix. Without this added perk, your plant may have stunted growth due to a lack of CO₂ nutrients.

It is best not to store clay media inside because they are porous and absorb any odor from nearby objects like garbage cans or old shoes.

It's best to buy clay from a store with high turnover so that there is less chance of bacteria growth, but if the clay media are sealed in plastic, this isn't as much of an issue.

How do I know how much clay I'll need?

When using clay pellets, it's important not to over-fill containers with expanded clay pellets because they can't be compacted to fit more. 

The amount of clay needed will depend on how many plants you are growing and what size container or pots you're using. The most commonly used clay size for indoor purposes like hydroponics is around 16mm (about the size of a nickel), and you'll need one pound per square foot. 

Some clay media come with nutrient solution pre-loaded and are meant as a complete product. In contrast, others need to be mixed with clay before use, or they will leach out their minerals over time.

You might find some sources suggest using more clay pellets than usual to compensate for the draining issues. Still, most growers say this isn't necessary- just use what's comfortable with how much water is being added each week.

How do expanded clay pebbles compare to other growing mediums?

There's no one best type of media- there are many different types on offer, with varying pros and cons!

Examples of hydroton clay alternatives include expanded shale or scoria (volcanic rock), vermiculite, coco coir fiber chips, coconut husks, and more.


An excellent media to use at the start of a plant's life cycle is Rockwool. Rock wool cubes can be purchased pre-potted with expanded clay pebbles as well. Still, some growers say they're not very good for long-term growth due to their tendency to break down over time and release chemicals into the media.

It is a sustainable and environmentally friendly medium.

It is not an organic material, but it's a good choice for those seeking to avoid pebbles or expanded clay because they prefer something more lightweight.

You can reuse Rockwool indefinitely as long as you never introduce any pests or diseases into the media. As a result, your garden will be safe from potential contamination!


A good alternative is perlite which also work fine. It has excellent water-holding capabilities but won't decompose like hydroton clay balls over time and underneath your potting mix.

Perlite works best for plants that prefer well-draining media or have sensitive plant roots systems. It can be mixed into potting mediums at any percentage you choose, depending on its intended use.

Lava Rock

There's lava rock too! They're not quite as popular because they don't hold onto nutrients as readily as clay does. Still, they do offer more benefits in terms of drainage than traditional media such as sand. They are PH neutral.

Lava rock is also considered a better alternative for plants that like to be more root-bound or those with shallow root systems. It provides air pockets in the potting mix, which increases airflow and drainage.

They are heavier than a pebble, so you will need to make sure your pots have adequate weight capacity if using this type of growing medium. In addition, they can break when handled too roughly, but their great usage makes them worth considering as an option.

Sphagnum Peat Moss

In addition to hydroton clay balls, there's sphagnum peat moss which has excellent water retention qualities. It does decompose over time, though, just not very quickly compared to clay pellets, so only use it where


Another excellent alternative for clay is hemp, an organic form of clay that is lightweight, virtually indestructible, and works well with clay-sensitive plants. What makes it a great alternative is that you can also use it as a mulch in your garden to help prevent weeds and retain moisture.

Coco Coir fiber

One of the most popular substitutes for clay pebbles is coconut fiber. It's a more environmentally friendly medium and sustainable option. Still, it also has some downsides - it breaks down quickly in acidic soils (such as pine or citrus) and doesn't stick to clay-sensitive plants as hemp does.

Are clay pebbles reusable?

Many pebbles are made of expanded clay, which means they can be reused as long as you don't crush them or use sharp tools on them. Just make sure to rinse occasionally, soak and sterilize them with isopropyl alcohol or peroxide.

Watch for any whitish residue on the top and rinse your pebbles after the gardening season with a pH-adjusted liquid for maximum sustainability.

Rinsing, soaking, and sterilizing your hydroton clay is also recommended, combined with isopropyl alcohol or peroxide to remove any residue from the plant life. It may be a time-consuming process but well worth it.

Add your base grow nutrient solution afterward, as needed. You may wish to use one-quarter strength of the base nutrient or add a 0.4 electrical conductivity solution.


Hydroton clay is an excellent choice as a medium because it provides aeration and nutrients that are crucial to plant growth. The hydroton also helps maintain an even temperature throughout the year, ideal for root system growth, while maintaining neutral PH levels.

Pebbles are an excellent option for hydroponic, urban, and city gardeners who don't have much space to grow in. The clay is lightweight and more accessible to carry than traditional soil. It also doesn't need to be dug up at the end of each season or year, as other media do.

Hope you enjoyed this guide with all of our tips about using clay as your garden's main ingredient. For more information on other media and growing systems and gardening brands, visit our blog.

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