Using Hydroton (Leca Expanded Clay Pebbles) to Grow Plants

Last Updated on January 10, 2019

Leca clay/Hydroton is a popular medium because it has more benefits and a few downsides. LECA or Hydroton is a standard medium used in Aquaponics, Hydroponics, and Aeroponics. We’ll discuss in detail about this medium in this post. From Introduction to pros/cons and do’s/donts.

What is Leca Clay?

Expanded Clay PebblesLECA Stands for “light expanded clay aggregate”, Also known as Clay pebbles or hydroton is a hydroponic substrate with units about the size of marbles or peanuts.

Hydrotron is a favorite choice of small producers using media bed or Dutch bucket techniques because of features like lightweight, easy to transplant & harvest, and easy on the hands.

Clay pebbles can be used in both hydroponic and aquaponic systems.

How is it made?

Leca/Hydroton is a processed ceramic lightweight aggregate produced by expanding selected clays in a rotary kiln fired to a temperature of approximately 1200°C. This process expands the material 4 to 5 times its original volume creating ceramic pellets with a cellular inner structure. It is Green, Anti-shrinkage, Internal curing, Lightweight, Sound, and Thermal Insulation and Fireproofing.

Hydrokorrel Specifications:

  1. Crushing Strength =3,1 n/mm²
  2. Density= 403 kg/m³
  3. Size: 8-12 mm

Uses of Expanded Leca Clay Pebbles

Hydroculture: Their neutral pH and excellent capillary action qualities make them a great hydroponic/Aquaponics medium. Typically used in flood & drain or ebb & flow growing systems. Preferred by horticulturalists for hydroculture, this product offers many advantages when compared to soil. The medium is clean, odor-free, reusable, and provides excellent aeration.

Leca is also a useful additive to Coco Medium and Soil when growing in Pot Culture and also anywhere where extra drainage is needed. Also Used in drainage layers in flower pots, roof gardens, for trees in an urban setting and sports grounds.

Substratum cultivation in professional horticulture and the cultivation of decorative plants: This highly porous growing medium is used to fill plant baskets and container gardens and provides good physical support for roots.

LECA prevents rotting, excess acidity, and soil pests. Great for aeroponic, NFT, and GHE water farm/Dutchpot systems.

How to Use Clay Pebbles: Do’s & Don’t

How to Use Clay Pebbles
Plants are easy to harvest in Hydroton

The Flood & drain and ebb & flow are the usually recommended methods for using these clay pebbles. Here are some do’s and dont’s to keep in mind while working with them. When using for hydroculture (Aquaponics/ Hydroponics/ Aeroponics):

  • If you’re using new hydroton, rinse it once with clean lukewarm water before using; it can be dusty and cause clogging problems in mesh filters or drippers.
  • Sometimes it floats! Nothing to worry here! When you buy a new one, some of the clay pebbles will float. It is normal till they soak up some water. These need to be held under water and made to fill up. Soak the pebbles for at least six hours or, even better, up to 24 hours. You can put something heavy on top to hold them down. The air should escape. Yes, the medium will be heavier but your plants won’t have to work hard to get to the water they so desperately crave.
  • Remove the dirt as far as possible from the plant
  • Spread a 3-4 cm thick layer of pebbles in the hydroculture pot
  • Place the plant in the pot and top up with until there is a water margin of 2cm. While topping up move the plant gently up and down so that the clay is all around the roots.
  • Try to keep an inch (or as much as possible) of dry balls on the top to protect the system from fungus and algae growth.
  • During the first week only apply water. Subsequently, add hydro-fertilizer.

Other Tips

  • Use clay pebbles as Seed starter: You can crush the medium to increase saturation or you can keep them whole, use small net pots, and cover the seed with a couple of pebbles. Misters set to bursts lasting four to 10 seconds every two or three hours will bring on germination. Just make sure you have soaked the pebbles beforehand. If you don’t have misters, manual feeding will work fine, too, as long as you don’t let the pebbles dry out.
  • Don’t reuse the pebbles without rinsing, soaking, or sterilizing with isopropyl alcohol or peroxide. Taking the time to do it right will save headaches later.
  • Never let the pebbles dry out. Ever. Period.
  • Don’t use a regular pot unless you have a dedicated water source. Using regular pots can sometimes lead to algae and draining issues.
  • Don’t use the pebbles as a substitute for soil outdoors. You can certainly use them in conjunction with soil but not as a replacement in your outside garden.

Pros of Hydroton

  • Good colonization for microbial populations 
    While grow stones are smoother than some media, they are not so smooth as to discourage colonization by microbes. The more surface area your media has the more bacteria it can support. Clay pellets have a good ratio of BSA and air space and one of the main reasons why they are the standard media available. Lava rock is even better and cheaper but some people don’t like working with it because it has sharper edges and is harder on your hands.
  • High pore space means fewer blockages
    Larger aggregates like hydroton, pea gravel, and crushed granite have much larger space between each rock or pebble than perlite, sand, and other small particles. While the biological surface area isn’t usually as high, the pore space is much higher.
    What does that mean? Larger pore spaces mean better percolation (flow of solution through the media). Hydroton rarely becomes clogged or blocked, so water drains very effectively. This makes it a great option for ebb-and-flow systems and aquaponic media bed systems.
  • Fairly recyclable & environment-friendly:
    They can last a long time. Just wash and reuse as many times as you need. You don’t have to worry about losing nutrients through numerous washes because there aren’t any to begin with. If they lose their usefulness, you can add them to the soil of your outdoor gardens to increase aeration and organic content. Compared to many media used in greater amounts that are more demanding of the earth’s supply, hydroton is very friendly to the environment.
  • Air-holding capacity to keep root zones oxygenated:
    The pores in the pebbles, the space between them, and their superior drainage function keeps air circulating so roots get plenty of oxygen. While it can’t rival perlite’s air-holding capacity (AHC), this grow media does have some capacity to hold air bubbles. Combined with the great percolation, hydroton’s AHC makes it difficult for problematic anaerobic zones to occur. You can crush them to increase water retention for use in the germination stage of growing.
  • pH neutral and rather inhospitable to bugs:
    With hydroton, you can rest a little bit easier about finding the proper pH balance. In Aquaponics, you want to make sure that your pH always stays under 6.3 and above 5.6. If they start to head outside of this range, you plant will start to be deprived of certain essential nutrients. pH imbalance may be harmful to fish and bacteria as well. Some hydroponic media are either acid or alkaline, which, while certainly manageable, can make having an ideal pH in you hydroponic garden a little more difficult. Hydroton is pH neutral, which means that you do not have to deal with any of these kinds of worries.
  • Easy to plant and harvest:
    Hydroton is a loose media, so it’s easy to transplant and pull plants out of after harvest. Don’t underestimate how much time this can save you in wrestling with plant roots and separating root balls from the media surrounding them.
  • Inexpensive (on Small Scale):
    They’re inexpensive since they are cheap to make and can save you money reusing them over years.

Cons of Hydroton

Since these can be somewhat pricey, it seemed fair to let everyone know of any possible Pros.

  • Fairly costly on large scale:
    It is extremely easy to work with, which makes it the first choice to use it on small scale. But, it’s a bit too expensive for most large growers to use it. However, there are some free alternatives to grow media with some downsides
  • Not suitable for cold outdoor climates:
    According to an observation, they’re not suitable for cold outdoor climates.  It seems that each time they have frozen (with water in them) the tiny channels and pockets fill with ice and create larger fractures within the clay pellet. Over time, Their crushing strength decreases and you can crush these with very little pressure from a thumb and finger. If it’s NEVER going to freeze these are still a top-notch option in my way of thinking.
  • Can be problematic with pumps and plumbing:
    Because pebbles float for the first few months until it’s been saturated, the pebbles can get sucked into filters or drain lines and cause blockages. If you don’t rinse and soak them properly before use, the dust from the clay pebbles can get into some of the mechanics of your systems and cause issues.
  • Water holding capacity leaves something to be desired:
    Their excellent drainage can also be a problem, making them quick to dry out. As, Clay pebbles don’t have good water holding capacity, or WHC. Since WHC is what allows a substrate to stay moist even after being drained, low WHC means that crops can get dry and wilted if not watered often enough. In some systems (with cooler climates, drought-tolerant crops, and/or constant flooding) this is not an issue. Growers who have high transpiration rates, water-needy crops, etc. will need to figure out a way to keep the substrate moist. That’s why it is mostly used in flood & drain or ebb & flow.
    Low WHC isn’t a big deal for most producers; just be aware of it and make sure you have frequent enough watering.

Alternatives & Comparison

Hydrocorn vs Hydroton

Comparatively, Hydrocorn is smaller, irregular in shape, and tends to settle into a more compact substrate. Hydroton is pH neutral. Whereas, Hydrocorn comes with an initial pH of anywhere in the range of 8 – 10. You need to soak with an acid solution for 4-5 days to lower the pH.

Hydroton vs Rockwool

Rockwool has more water retention capability and is considered great for seed starting. Unlike Hydroton, Rockwool is not pH neutral. They come with a high pH and need to be soaked in water before using. They are also not considered eco-friendly. Rockwool is also not recommended to use in aquaponics as it can cause irritation to fish or they can consume the fiberglass.

Hydroton vs Perlite

Perlite is relatively inexpensive and lighter in weight as compared to Hydroton. Perlite is not recommended for an ebb and flow system as it will wash away too easily during flooding. both are made to hold water and have a certain amount of water wicking ability. Although perlite has more cracks and crevices, Hydroton stays moist longer because of its higher absorption ability.

Buying Tips: Where & How to Buy

You should be able to get the clay pebbles at a gardening center, garden shop, places where you can buy large shrubs, bushes, and even tree’s.

Check Before buying: It can be any kind of rock really, just do a vinegar test. if you put a handful of the rock in a glass of vinegar and they bubble, then it has too much limestone and you shouldn’t buy it.

Online Resources

GROW!T Clay Pebbles are available on Amazon in 10, 25, 40-liter bags. They are less likely to break and cause system issues. They are pre-washed.

Leca Clay Grow Media has uniform pebbles in a 2 lbs bag with mostly five-star reviews.

Check more growing medium alternatives with their ups and downs here.

Have any question? Feel free to ask in the comments. You can share your own experiences using these little red pebbles, that may add value to information and knowledge of others. & if you have any friends who want to know more, please share this article with them. Thanks for reading!



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There are 3 comments

  1. Hello! Do you think that the size of the clay pebbles matters for growing plants? I’ve seen some that are labeled as “giant”. They’re advertised as 15-25mm. I’ve seen others labelled as 8-16mm.



    1. Hi James,

      Thank you for your comment. Yes, size of clay pebbles does matter.!
      Small particles have more Biological Surface Area and Nutrient holding capacity, easier to Plant and move. However, its cons are Compaction Solid accumulation
      While large pebbles have higher void space (Large pores), better percolation, are easy to clean but have Lower Biological Surface Area.
      Check this article for more information



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