Why clay pebbles are one of our top picks for small growers
Clay pebbles or hydroton (sometimes referred to as LECA—light expanded clay aggregate) are a hydroponic substrate with units about the size of marbles or peanuts. Because they’re so lightweight, easy for transplanting and harvesting, and easy on the hands, they’re a favorite of small producers using media bed or Dutch bucket techniques. Clay pebbles can be used in both hydroponic and aquaponic systems.
Read on for the pros and cons of using expanded clay pebbles like hydroton in your hydroponic or aquaponic systems.
Pros of hydroton
1) 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), even when biofilms from algae and microbes cover the surfaces of the media, and even if some debris is captured in the pore spaces. 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.
2) Some air-holding capacity to keep root zones oxygenated
While it can’t rival perlite’s air-holding capacity (AHC), this grow media does have some capacity to hold air bubbles. Combined with great percolation, hydroton’s AHC makes it difficult for problematic anaerobic zones to occur.
3) Fairly renewable & environment-friendly
Not much clay is used to make a cubic foot of hydroton, and clay is abundant, so most people consider it an environmentally-friendly medium to use. Compared to many media used in greater amounts that are more demanding of the earth’s supply, hydroton is very friendly to the environment.
Although hydroton is a mineral and not considered a pollutant, we still don’t want it to end up in a landfill. Luckily, they are reusable almost indefinitely. You usually want to rinse any built up silt or organic matter from it before reusing it, but unless you have an extreme salt build up in it, you can reuse it many times.
5) 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.
6) Good colonization for microbial populations
While grow stones are smoother than some media, they are not so smooth as to discourage colonization by microbes. As you may know from our biological surface area resources, BSA provides habitat for the microbes which make nutrients from organic sources like fish feed available to plants. Less BSA means fewer microbes, which means a less responsive and less stable system. Though possessing less BSA than some media, this grow medium still offers high BSA.
Cons of hydroton
1) Water holding capacity leaves something to be desired
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 irrigation) 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.
Low WHC isn’t a big deal for most producers; just be aware of it and make sure you have frequent enough watering.
2) Fairly costly
Hydroton is extremely easy to work with, which makes it a first choice for many small growers, but it’s a bit too expensive for most large growers to use it.
3) Can cause problems with pumps and plumbing
Because hydroton floats for the first few months until it’s been saturated, the pebbles can get sucked into filters or drain lines and cause blockages.
Tips on using hydroton
Hydroton is one of our first recommendations for small growers using media bed systems like the Hughey Aqua Farm or Dutch buckets. They’re easy to use and easy to source (Hort Americas is also a trusty supplier).
Tip: If you’re using new hydroton, remember to rinse it once before using; it can be dusty and cause clogging problems in mesh filters or drippers.
Need more info on hydroponic and aquaponic substrates?
The substrate decision can be overwhelming. That’s why substrate experts Chris Higgins and Farmer Tyler from Hort Americas presented an entire course on choosing the best hydroponic substrate.
In the Choosing a Substrate course, learn about:
- Holistic decision making
- Special considerations for choosing a substrate
- Organic substrates
- Plugs for hydroponics
- Media for microgreens