Popular Types of Hydroponic Growing Media

One of the first questions to pop up from new soilless gardeners is “What type of growing media should I use for my hydroponic project?” This topic is often subjective, because there are many types of hydroponic growing media out there. In our experience, the answer is often “It depends.” Things such as price and space limitations are key factors when making your decision. Some other less mentioned factors include impact on environment and availability. You’ll find that several of the options listed below are readily available from local sources, while other hydroponic media can only be bought from specialty stores and online sources. Here’s a growing media guide to help you decide what works for your hydroponic setup.

Types of Growing Media

 

Hydroton

Hydroton is one of the most widely used types of hydroponic growing media out there. You’ve probably seen it in pictures of hydroponic systems (disregarding the fact that it’s our feature image). Hydroton is also commonly referred to as expanded clay pebbles or LECA, which stands for light expanded clay aggregate. Hydroton has several benefits that make it a popular option for hydroponic growers.

Hydroton, one of many popular types of growing media

Pros

Nutrient/Water Circulation

Hydroton promotes nutrient circulation to each of your plants. Hydroton is one of the larger types of media, and as a result there are large spaces left between the pebbles. What this means is that the nutrient solution will flow and drain more easily in the medium and reach your plants with minimal blockages or clogs.

Air Circulation

Due to the porous structure of expanded clay pebbles, air circulation is superb. One thing is for certain with this medium, your root system will receive plenty of oxygen.  This also adds to the superior drainage functionality of hydroton.

Reusable

Another positive regarding hydroton is its reusability. Clay pebbles last a long time, so you can always rinse off any built up gunk and reuse them. Once you’re done using them in your hydroponic grow, you can add them to other media, soil or soilless, and provide some additional aeration.

Neutral

If you want one less thing to worry about when monitoring your solution’s pH levels, hydroton is pH neutral.

Pest/Fungus Resistant

Pests and fungus don’t have a great reason to hang out in this growing medium, especially due to the excellent drainage (and poor water retention, but we’ll get to that).

Microbial Growth

LECA promotes some positive microbial growth due to its porous nature. While you certainly don’t want bacteria negatively affecting your plants, there are positive microbes out there. Similar to how our digestive system contains gut flora as part of a healthy GI tract, some microbes out there help keep plants healthy as they grow.

Cons

Poor Water Retention

All of this talk about superior solution circulation and drainage comes with a caveat: hydroton has poor water retention. As a result of this, certain types of hydroponic systems will run into issues with maintaining a moist environment for plant root structures after solution is no longer actively flowing. For example, in an ebb and flow system, after the nutrient solution has drained away, hydroton will quickly begin drying out.

Preparation

Expanded clay pebbles require some initial preparation. You may notice that some clay pebbles appear red. This fine dust is actually iron oxide and is typically present in a fresh bag of pebbles, which will require rinsing. If you don’t do this, you can expect crap to build up in your water pumps, tubing, pots, and reservoirs.

Expensive

Hydroton is relatively expensive. A small bag may not seem too pricey, however for larger scale operations, it could get expensive to buy many bags of clay pebbles. You do need to factor in its reusability, which can make the initial upfront cost worth it.

Environmental Impact

While ecofriendly in the sense that the medium is both reusable and clay is abundant, the methods used to obtain clay are less so. Unfortunately clay is typically obtained through open-pit mining aka strip mining. For this reason we hope you’ll consider some other options if you’re operating a larger hydroponic gardening operation.

Heavy

Hydroton runs on the heavy side, so if you need large quantities you better start lifting and saving your allowance for the shipping costs.

Rockwool

Rockwool is a lightweight material made from molten rock fibers. For hydroponic purposes these fibers are arranged into convenient shapes such as blocks, slabs, or cubes in which a plant can be placed. Interestingly, rockwool was originally designed to be used as insulation material. Even today rockwool is sometimes used in construction, for instance as a firestop. However the material is expensive and often not economical for construction projects. Hydroponic products out there utilizing rockwool are often quite versatile. Rockwool products sometimes vary fiber density throughout the product to promote certain characteristics such as aeration or water retention.

Pargro Quick Drain Blocks, 4" x 4", Wrapped, case of 72

Pros

Nutrient/Water Circulation

The fibrous material that rockwool is comprised of makes for excellent circulation of your nutrient solution. As I briefly mentioned above, rockwool products often vary fiber density throughout the structure of a given product, offering flexibility in how much solution reaches certain parts of your plant. Preferably only the bottom of your rockwool should be exposed to solution, and then wicking will draw the solution further up the medium without making it too wet.

Air Circulation

Along with positive liquid circulation, rockwool promotes air circulation. Assuming your rockwool medium isn’t completely submerged, there should be plenty of oxygen reaching your plant’s root system.

Water Retention

Rockwool is great at retaining water that has been circulated through the medium. For systems like ebb and flow where your medium is exposed to solution only temporarily, this is excellent. The retained solution will continue to provide nutrients and water to your root system. However you want to make sure your system has plenty of airflow, otherwise your plants may get too much moisture and not enough oxygen.

Microbial Growth

While naturally inert, rockwool provides a good environment for positive microbial growth.

Cons

High Environmental Impact

The process used to make rockwool fibers utilizes Basalt rock and chalk to make a material that doesn’t occur naturally. This hybrid material is considered non-biodegradable and there isn’t a great way to dispose of said used material. Chances are your disposed material will just sit in a landfill for eons. Hopefully this bothers you somewhat and you’ll consider other hydroponic growing media.

Not Easily Reusable

Rockwool is certainly capable of being reused, however you’ll have to go through a process to do so. Generally this means removing all preexisting roots via soaking and then sterilizing all of the media with enzymes.

Susceptible to Pests

Due to its excellent water retention qualities, rockwool has the unfortunate side effect of attracting certain types of pests. For instance, fungus gnat larvae thrive in rockwool. The best way to avoid this is by being careful not to oversaturate your medium.

pH Unbalanced

Rockwool has a high pH, sitting around 8, due to formation of lime on the fibers during manufacturing. The best way to remove this lime buildup and drop your rockwool’s pH down to neutral is through soaking the rockwool in pH balanced water of around 5.5-6.0. Much like other media, the soaking process can take anywhere from twenty minutes to a couple hours, depending on how thorough you want to be. You’ll continue to test and soak the medium until you’ve reached the desired pH. We’ll likely go into a full post regarding this process.

Hazardous

Fresh blocks of this medium can contain dust that is harmful if inhaled, swallowed, or if it gets into your eyes. Much like asbestos or similar materials containing fine man-made particles, rockwool dust can stick to your lungs and cause respiratory issues. Not to mention rockwool is a skin irritant. However many rockwool products come wrapped to make handling easier. We recommend using a respiratory mask, gloves, eye wear, and most importantly caution when handling this material.

Growstones

Growstones are gaining popularity among hydroponic folk as an alternative to hydroton. These have a few traits that make them more appealing than hydroton. Many report that growstones work as well if not better than hydroton. Like other large growing media out there, they are often used in a mixture with popular small media, such as coco fiber, to add better air circulation and accommodate specific plant needs.

Pros

Nutrient/Water Circulation

Similar to hydroton, growstones provide superb solution circulation due to their shape. However there is potential for drainage problems. Due to their irregular shape you’ll want to make sure that no blockages are present; this doesn’t really seem to be much of an issue though.

Air Circulation

Growstones are another very porous growing medium. Air circulation shouldn’t be much of a problem if you use this. Again, air circulation helps with drainage as well.

Reusable

Like other larger growing media, growstones are reusable. Potentially. I say potentially because you can run into several issues when trying to extract, rinse, and sterilize this medium for reuse. See the cons section for more detail.

Very Environmentally-friendly

Growstones are made from 100% recycled glass materials. What this means is you get environmentally-friendly media from a source that is essentially limitless. Compare this to hydroton or perlite, which are strip mined, and its a no-brainer for the eco-conscious grower (and shouldn’t we all strive to be that type?). The recyclable nature and abundance leads into the next point…

Inexpensive

Not much more needs to be said for this point. Growstones are relatively inexpensive for reasons mentioned in the last point.

Lightweight

The primary material in growstones is recycled glass. As a result, the medium itself is pretty light compared to other media.

Cons

Preparation

Similar to hydroton, growstones require some preparation. Growstones are frequently covered in a fine glass dust which needs to be rinsed off before use in your system. Much like any other fine particles, this glass dust will clog your system’s various inner workings if you don’t spend some time to rinse the medium before use. They also require preparation to account for the next point.

pH Unbalanced

When your order of growstones first arrives it will need to be pH adjusted. Growstones generally come out-of-the-bag too basic for growing (a pH of 8+ is not uncommon). The first part of pH balancing growstones is already taken care of if you rinse them off to remove the fine dust. Then you’ll need to place the growstones in a bath of pH balanced water (something in the range of 5.5-6.0) for twenty minutes. Some resources even suggest soaking the growstones overnight in this bath. Test the pH of the bath and, if necessary, continue soaking your growstones until the pH stabilizes.

Brittle

Due to their composition, growstones are more brittle than other hydroponic growing media. As a result, too much fiddling with your growstones can lead to buildup in your hydroponic system as growstones break into smaller pieces or fine glass dust.

Potential Sharp Edges

Because of their brittle nature and recycled glass composition, growstones can become quite sharp. Some caution is advised while handling this growing medium, though we hope that this particular reason doesn’t put you off from considering growstones.

Sticky Reuse

While one of the pros touted the reusability of growstones, it also mentioned that there’s a caveat. Root systems have a habit of sticking to growstones, which can make extraction of your medium difficult when you decide you want to reuse it. Any roots remaining on the medium need to removed, otherwise you risk transferring diseases from your old root system to your new plants. On top of that, as these pieces of root decay, they release CO2, which can kill your new root systems. Typically an enzyme wash will handle any remaining roots clinging to the growstones, followed by several days of drying to completely sterilize your growstones before reuse.

 

Like what you’ve read so far? If you’re looking to purchase a particular growing medium, please consider our Growing Media Products at the bottom of this page

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Coco Coir/Coco Peat

Coco coir (or coco peat) is a by-product of coconut processing and is made up of the inner shell of coconuts, generally what we would consider the husk. In the past, these parts of the coconut were simply discarded because there was (supposedly) no use for them. However coco coir has many characteristics that make it ideal for use as a soil substitute or hydroponic growing medium, and the medium has become increasingly popular in recent times. There are two different types of coco fiber out there, white and brown. For hydroponic usage, brown coir is the way to go and is what we’re referring to from now on.

Coir, an example of popular hydroponic growing media

Pros

Water Retention

One positive characteristic of coco coir is that it’s great at retaining water. Coco coir retains water nearly seven times its dry weight. As always though, when water retention is high you can run into other issues as outlined further down.

Air Circulation

As a standalone medium, coco coir provides your plants with easy access to oxygen because of its fibrous nature. With its great aeration quality, coco coir is often mixed with other growing media. These mixtures optimize the amount of oxygen reaching the root system of your plants.

Easy Transition From Soil

Soil gardeners looking to make the leap to hydroponic systems will find that coco coir is an easy medium to work with. It has many similar qualities to soil including consistency.

Very Environmentally-friendly

Coco coir originates from the husks of coconuts. It’s easily bio-degradable and can be incorporated into other gardening projects when no longer needed for your hydroponic grow. Furthermore, the ingredients are by-products of coconut processing, giving this medium two green thumbs up from us environmentally.

Nutrient Supplementation

Coco coir naturally contains potassium, a key ingredient for plant growth. As a result, your plants will gain some supplementation from this medium.

pH Buffering

One nice aspect of this medium is that it tends to naturally buffer pH towards the acidic side. Coco coir pH can vary between brands, but generally you can expect sub-neutral pH levels. If you don’t know, plants thrive in an acidic environment, which promotes nutrient uptake by your roots.

Microbial Growth

Beneficial microbes can thrive in coco coir. However make sure you properly prepare and supplement your medium. Microbial growth, much like your plants, doesn’t like high salinity which can be present in fresh coir.

Cons

Preparation

Fresh coco coir may require hydration and rinsing. The husks from coconuts contain large amounts of sodium which can negatively impact your plants and cause buildups in your hydroponic system.

Not Easily Reusable

It’s definitely possible to reuse coco coir. However like most finer mediums, you’ll find that it can be a pain in the ass. We won’t repeat what’s already been mentioned for other reusable media, but expect to soak your medium in an enzyme bath for a couple weeks to sterilize.

Cal-Mag Deficiencies

Coir tends to run deficient in both calcium and magnesium. Both of these are necessary for successful plant growth. Expect to invest in some Cal-Mag if you’re going with this medium.

Susceptible to Pests

There are several sources that claim coco coir is resistant to various pests, however this isn’t completely true. Its water retention abilities make coir susceptible to pests, particularly fungus gnat larvae. We’ll discuss how to handle these and other pests in a later article.

More Expenses When Mixed

 Coir is a commonly mixed medium. If you plan to go this route, expect to pay more for various growing media.

Vermiculite

Vermiculite actually comes from the Latin word “vermiculare” which means “to breed worms.” This is because, when heated, vermiculite expands into worm-like strands. It is a natural mineral that is used in various industries outside of gardening. It is a silicate substance much like mica. Vermiculite comes in many different grades, however coarse vermiculite tends to be what’s used for horticultural purposes.

Vermiculite, a popular type of growing media

Pros

Water Retention

Vermiculite has excellent wicking capabilities. It’s also sponge-like in its ability to retain water. However be careful not to overwater as drainage isn’t as good as, say, perlite.

Neutral

This medium is generally pH neutral. Depending on the source and quality, there’s a possibility it’ll run basic. Make sure to do your research and don’t be afraid to pay a little extra for higher quality vermiculite.

Cons

Easily Overwatered

Unlike perlite, vermiculite actually absorbs solution into its particles much like a sponge. If utilizing 100% vermiculite, this could be setting you up for root rot. This is where the common mix of perlite and vermiculite (and even coco coir) comes in. Mixtures provide an ideal combination of moisture retention, drainage, and airflow.

More Expenses When Mixed

Vermiculite is a commonly mixed medium. Expect to pay more to create your own custom mixes.

Messy

Vermiculite can get a little messy, especially due to its sponginess. For certain systems (deep water culture or ebb and flow) you run the risk of clogging components.

Perlite

Perlite is a volcanic glass that is heated to extreme temperatures to cause it to expand into a lightweight material full of microscopic air compartments. Sounds pretty out there, but you may have unknowingly noticed perlite in your potting mixes. If you look in many potting mixes, you’ll notice white, rice-like grains scattered throughout the mix. This is perlite, and it helps keep soil aerated and aids in drainage. However, perlite is also an example of growing media for hydroponic usage. It can be used alone or mixed with other growing media.

Perlite, an example of popular growing media

Pros

Air Circulation

The microscopic compartments mentioned in the overview make perlite highly porous. Expect plenty of oxygen flow to your root systems.

Drainage

Unlike vermiculite, perlite doesn’t actually absorb the water into itself. Instead it retains water within the spaces that occur on the medium. The composition of this medium and the excellent air circulation make drainage a non-issue.

Pest/Fungus Resistant

The air circulation and drainage properties of perlite make it resistant to fungus and pests. Typically these headaches both rely on extended water retention, which perlite by itself does not do well.

Neutral

Perlite is pH neutral, which is a positive in my book.

Cons

Poor Water Retention

Now perlite does retain a small amount surface moisture, however it’s not spongy like some of the other growing media discussed. This surface moisture is great for maintaining a humid environment, but there isn’t enough moisture to nourish plants thoroughly.

Environmental Impact

Unfortunately for the environmentally conscious out there, perlite is kinda bad for the environment. Similar to hydroton, perlite is strip mined. That being said, both of these growing media are still extremely popular.

More Expenses When Mixed

Perlite is commonly mixed with vermiculite or coco coir. Expect to pay more to create your own custom mixes.

Hazardous

Perlite can create fine volcanic glass particle dust. This dust is an irritant if inhaled, ingested, or if it gets in your eyes. Like similar growing media, we suggest a respirator, eye wear, and gloves when handling perlite.

Messy

This medium comes in a variety of grades. Depending on how fine a grade you purchase, perlite can clog hydroponic systems. In particular deep water culuture and ebb and flow systems may run into issues, as this lightweight material can shift around your plants or be swept into components.

Starter Plugs

Starter plugs are small samples of growing media that are used primarily for germinating seeds and for plant cloning. These plugs can be bought with either a hole available for whatever seed the gardener desires, or with seeds already incorporated into the plug. This medium provides an ideal amount of moisture and oxygen to promote propagation in plants. While extremely useful, starter plugs’ purpose are limited to the beginning of the life cycle of plants.

Super Starter Plugs, 72 Pack

Pros

Great for Germination
Great for Cloning

Cons

Limited Usefulness

Starter plugs aren’t useful for the majority of a plant’s life cycle.

 

Alternative Growing Media

This is by no means a comprehensive list. Growers get creative and utilize all sorts of media such as gravel, sawdust, sand, rice hulls, and more. However this guide should provide plenty of information on some of the more popular types of hydroponic growing media. Do your research and determine what works best for you!

 

Growing Media Products

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Grow!t Clay Pebbles (Hydroton)

Geolite Clay Pebbles (Hydroton)

Pargro Quick Drain with hole (Rockwool)

Roots Organics Soilless Hydroponic Coco Media (Coco Coir)

CYCO Coco Pearl (Coir and Perlite Mix)

Super Starter Plugs

 

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Attributions (these users in no way endorse the material posted on this site):
Hydroton(featured image) By Lucis (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Hydroton Cups Photo Credit: thewritingreader Flickr via Compfight cc
Coir By Fotokannan (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Vermiculite By I, KENPEI [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

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