Economical Hydroton Clay and Expanded Clay Pellets Explained!

LECA Clay pebbles

Hydroton? Expanded clay pellets, also referred to as in reference to the popular brand, seem like clay with a fancy name at first glance.


Upon initial exposure, many beginning hydroponists hear the name and think the product is just for the pros then see the appearance and think hydroton is just overpriced rocks.  Which impression is correct?  It isn’t necessarily easy to say and it can really depend on how they’re used.




What are Hydroton pellets?

Hydroton in Net Pots
Hydroton in Net Pots



To really get a good idea of what these pellets are, we need to actually look at a third common name for them:  Lightweight Expandable Clay Aggregates (LECA).  Long ago people realized that some kiln-fired clays actually expanded (think bread rising to get a good mental image) and we’ve been using these clays as a building material since ancient times.  The expansion of the clay allows for some unique properties, such as a hard surface with low density and a porous texture.


Visually, expanded clay pellets have the size, shape, and appearance of a cocoa powder dusted truffle.  Don’t leave them around your child or spouse without warning!  Their circular shape is actually pretty critical for one of their most appealing properties – aeration and water flow.  It all comes down to contact surface area math, which is much more easily explained via a diagram:


In the 2D diagram, you can see how easy it would be for water to rise up into or fresh air and mist to pass through the completely settled clay circles.  In the real world, the expanded clay pellets aren’t perfectly spherical but will settle in a very similar fashion.




How are Hydroton pellets used in hydroponics?

Hydroton pellets are used in many different types of hydroponics systems.  Fundamentally, they are a support medium for the plants’ roots and are often placed in net pots to provide a full structure that otherwise wouldn’t be so heavily available.  The Dutch bucket system also regularly features Hydroton pellets.


These clay pellets can also be used readily with aquaponics as the clay can quickly become home to some beneficial life for your aquaponics ecosystem.  This is also why people will often give you the advice to thoroughly wash your expanded clay pellets before using them in new systems!




What are the benefits of using Hydroton pellets?

Roots growing through LECA clay Pebbles
Roots growing through Hydroton clay Pebbles, Source


As mentioned earlier, the round shape of the expandable clay pellets gives way to more open airflow (and water access).  This also gives us the advantage of reducing the chance of root rot as the roots not in contact with the water have a better chance of drying out safely.


Yet, if we just needed something a bag of round marbles would do!  So, let’s look at some of the other advantages of using Hydroton pellets that separates them from the average sphere:


Water Holding – In the high-heat kilning process that makes our lightweight expandable clay aggregates the clay… expands!  This expansion creates small holes in the clay pellets that hold water that slowly releases.


Beneficial Bacteria – These same holes can eventually become the homes of beneficial bacteria for use in your aquaponics systems.


Reusability – Once the aforementioned bacteria is cleaned out the clay pebbles can be used again in another system.  They don’t break down easily unless a strong force is applied to them.


Natural Aesthetic – Growing plants without soil is, for 99% of plants, a bit unusual and can add a somewhat clinical feel to plants.  Hydroton pellets give retail consumers and hobbyists looking for an indoor conversation piece a chance to have a “natural environment” aesthetic.


Beginner Friendly – They are beginner recommended and come in many commercial kits, such as the   succulents kit, specifically designed for the beginner.  When using these, it is hard to go wrong if you just use the instructions and read about what you are doing.




…And the Cons?

In nearly every situation where you might want to use Hydroton pellets, you could use something else – perhaps vermiculite, pebbles, or even the marbles we mentioned above!  So, let’s look at some of the downsides as well so you can make an informed decision about your purchase:


Variable Sizing – Unless the company you purchase from sorts the pellet sizes very well, any source of expandable clay pellets is going to have both small and large pieces in it.  The smallest pieces are likely to sneak through your net pots and end up in places you don’t want them.


Moisture Theft – In some limited situations, the pores in your clay pellets may actually soak up the moisture from your roots instead of giving their own excess moisture to the roots.  Always check your systems and perform routine root checks!


Bacteria Transport – What is good in one system might not work in another.  The same property that makes these good at providing good bacteria for your aquaponics systems can also cause a lot of trouble when taking used pellets and transporting them to another system.  Be sure to wash them thoroughly and soak the pellets in a bath that includes ethanol before putting used pellets into a new system!




Final word on Hydroton

Hydroton pebbles and other brands of expanded clay pellets can be a part of a complete hydroponics or aquaponics system.  Overall, they have very few downsides and are obtainable from just about any hydroponics supplier.  While Hydroton is synonymous with the product for a reason, be sure to check out our expanded clay pellets product review page for more insights.  If you know that you want to use Hydroton pellets in your design, you’ll probably also want a net pot to put them in.  Good luck with your system designs!



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John Alexander is a writer, English language educator, and plant enthusiast. After graduating from the University of Tennessee in Knoxville, he began working in labs filled with plants - identifying their seeds, counting their pollen, extracting their DNA, and (of course!) watering them as needed. Nowadays, he is focused more on words and language, whether that be teaching or writing.