When choosing a hydroponic growing medium, you want to choose one that’s easy to handle, right for your plants’ needs, right for you personally, and ultimately matches your design/system.
And luckily for you, the hydroponics extraordinaire, there are plenty of mediums that have been proven to work in hydroponic systems.
So to find out which one will work for you, explore the mediums below, explore our Hydroponics Hobby Center, and get a feel for the characteristics, popularity, advantages, and disadvantages of each one.
And remember, hydroponics is a relatively new field and is truly a trial and error process. Do your own experiments and mix and match as needed!
Most Common Hydroponic Mediums: Rockwool, Coco Coir, LECA, Perlite, and Vermiculite.
Jump To: Considerations for Mediums in Each Hydroponic System
All Hydroponic Mediums:
- Air
- Coco Coir
- Composted and Aged Pine Bark
- Floral Foam
- Growstone Hydroponic Substrate
- LECA
- Oasis Cubes
- Peat Moss
- Perlite
- Pine Shavings
- Poly (Polyurethane) Foam Insulation
- Rice Hulls
- River Rock
- Rockwool
- Sand
- Vermiculite
- Water Absorbing Crystals (Water Absorbing Polymers)
Air (No Medium)
While it’s pretty uncommon, there are certain situations where a growing medium isn’t needed. In these cases, your plant’s roots are either large enough to fill the entire “hole space” or are supported by other means. Such is the case in most aeroponic systems, where a “cloning collar” holds the plant in place and keeps light from penetrating your reservoir (thus not needing a growing medium).
- Medium Characteristics: NA
- How Commonly Used: Isn’t common amongst hydroponic growers.
- Hydroponic Systems: Aeroponic systems are generally the only time this works. However, if your roots and stem/plant base are large enough, they may be able to support themselves (and block out light from getting into your reservoir).
Main Pros: The main benefit to not using a growing medium is that it’s one less thing you need to worry about (aka you don’t have to provide or buy anything extra). There’s also the added benefit of not having to get your hands dirty.
Main Cons: the downside to air, of course, is that you don’t have an extra support system or a way to hold in moisture. Your plants also need to be a certain size before it’s even an option.
Coco Coir
Coco coir is a sustainable product that comes from the outer husk of coconuts. As one of the most popular growing mediums in existence, coco coir holds moisture extremely well, has a neutral pH, and is completely reusable. Additionally, as manufacturers are able to break the husks into smaller pieces, coco coir has several varieties/sizes to choose from — including “coco chips,” “coco pith or peat,” and “coco fiber.”
If you’d like a more in-depth assessment of coco coir, read our Coco Coir Hydroponics Guide to learn more.
- Medium Characteristics: Coco chips resemble small wood chips while coco fiber resembles potting soil. Depending on what product you buy, the size and shape of the coco will differ.
- How Commonly Used: One of the most (if not the most) popular growing mediums in existence.
- Hydroponic Systems: Good for any hydroponic system as there are several sizes to choose from.
Main Pros: Coco coir is simply unmatched as a growing medium due to its adaptability. It’s renewable, moisture-retentive, pH neutral, uninviting to insects, easy to handle, and great for root aeration.
Main Cons: One downside to coco coir is that it can be a little hard to find at brick-and-mortar stores. However, as most shopping is done online anyway, that shouldn’t be too much of a problem.
Composted and Aged Pine Bark
Pine bark will work well as a growing medium, but because it uses up nitrogen as it starts to decompose, it hasn’t been as popular as other mediums (although composted and aged bark greatly reduces this concern). Once considered a waste product, pine bark is made from shredded bark and comes in all shapes and sizes.
- Medium Characteristics: Small, shredded pieces of bark that are easy to handle.
- How Commonly Used: Not commonly used in hydroponic systems.
- Hydroponic Systems: Best for DWC and NFT systems.
Main Pros: Much like coco coir, pine bark has several size variations, holds moisture well, and has good aeration.
Main Cons: When not using composted or aged pine bark, nitrogen usually has to be supplemented. Additionally, because pine bark is so light, it has issues “floating up” in certain systems (such as flood and drain systems).
Floral Foam
Floral foam isn’t popular in hydroponics, but it can be used nonetheless. While it does work great in certain systems, it becomes waterlogged and has a bad habit of breaking apart and getting into your reservoir.
- Medium Characteristics: Typically a green foam that comes in round or square blocks; has a soft, squishy feel to it, and is often used in floral arrangements.
- How Commonly Used: Not a commonly used medium for hydroponics.
- Hydroponic Systems: Best for DWC systems.
Main Pros: Easy to find, easy to manipulate the material, absorbs water easily.
Main Cons: Becomes waterlogged and breaks apart too easily.
Growstone Hydroponic Substrate
Made from recycled glass, Growstone Hydroponic Substrate is a combination of clay and shaped marbles. Resembling irregularly shaped grow rocks, they’re a pretty popular grow medium in the hydroponic community. Not only do they have excellent aeration and moisture retention, but they’re light, porous, completely reusable, and have excellent wicking capability.
- Medium Characteristics: Lightweight, porous, and unevenly shaped medium that resembles grow rocks (and surprisingly not sharp even though it’s made of glass).
- How Commonly Used: Fairly popular amongst hydroponic growers.
- Hydroponic Systems: Does well with DWC, Drip Systems, Ebb and Flow, and Wicking Systems.
Main Pros: One of the more unique features of this medium is that it has a really great wicking capability and can wick water 4 inches up from the water line.
Main Cons: Because of the substrate’s wicking ability, there is a chance of “stem rot” if the water continually saturates the bottom stem of your plant.
LECA
LECA stands for “Lightweight Expanded Clay Aggregate” (also referred to as clay pebbles, grow rock, and/or other names such as Hydroton) and is a great hydroponic medium. Heavy enough to support your plants and light enough to not crush them, LECA is reusable, moisture-retentive, and pH neutral.
- Medium Characteristics: Round, reddish-brown, irregularly shaped clay pebbles that have a black interior with porous holes on the outside.
- How Commonly Used: One of the most common mediums used and can be found at almost all hydroponic stores.
- Hydroponic Systems: Great for DWC, NFT, Ebb and Flow
Main Pros: Perfect weight, has just enough wicking ability, porous, and is completely reusable.
Main Cons: Won’t work well for setups that need good water retention or for “starting” your plants (better for seedlings and up).
Oasis Cubes
Oasis cubes (and other similar products) are usually used as starter media, but there’s no reason they can’t be pulled apart and used to fill up your grow container (such as a net cup). Similar to rockwool cubes, they hold in moisture really well and have tiny spaces between cells that allow for additional oxygen and aeration.
- Medium Characteristics: Small fuzzy cubes with a small hole to insert your seed(s).
- How Commonly Used: Fairly common for starting seeds.
- Hydroponic Systems: Good for Grow Beds, Starter Trays, DWC, and NFT.
Main Pros: While they are similar to rockwool cubes and make excellent starter cubes, they won’t become quite as waterlogged.
Main Cons: Made primarily as starter cubes to germinate your plants.
Peat Moss
Peat moss is a type of growing media that’s produced in peat bogs. As Sphagnum moss grows, it eventually falls off into a bog, where it slowly develops “layers” and “partially” decomposes. The bog is then drained and the peat moss is collected, processed, and sent to consumers. Mostly used for starting seeds, peat moss has excellent water retention and is fairly inexpensive.
- Medium Characteristics: Resembles brown, fluffy soil. Typically is shipped/bought in bricks or loose in bags.
- How Commonly Used: Peat moss is commonly used in hydroponics but is mostly used for starting seeds.
- Hydroponic Systems: Great for grow trays and grow beds. Can also be mixed in with perlite or coco coir to make a usable medium for DWC, Drip Systems, and Wick Systems.
Main Pros: Peat moss has excellent water retention and is fairly inexpensive.
Main Cons: Despite its appearance, peat moss decomposes over time and compresses itself around your plant’s roots, choking off its oxygen supply. It’s best to mix it with coco coir to avoid this. Additionally, the process to extract it from peat bogs is extremely destructive and often removes century-old layers of moss.
Perlite
Able to be mixed in with other hydroponic substrates or used by itself, perlite is a great growing medium that’s lightweight, absorbent, and porous. Additionally, as it’s found in most garden nurseries (due to its use in potting soils), perlite is easy to find and readily available.
- Medium Characteristics: Soft, white substance that expands as it absorbs water.
- How Commonly Used: Fairly common amongst hydroponic hobbyists.
- Hydroponic Systems: Drip systems, Wick Systems, and DWC when mixed with other mediums. Probably shouldn’t be used in ebb and flow/flood and drain systems.
Main Pros: Good wicking ability, neutral pH, lightweight, absorbent, and porous.
Main Cons: Usually not used by itself because of how lightweight it is (often floats to the top of your system). Additionally, it’s not the best to handle due to how dusty it can be when dry.
Pine Shavings
While pine shavings aren’t common in the “hobbyist” community, they work great for commercial drip systems. Not only are they inexpensive, but they’re lightweight, easy to handle, water retentive, and can be found almost anywhere.
- Medium Characteristics: Small, lightweight shavings that resemble pencil shavings.
- How Commonly Used: Not common amongst hobbyists but fairly common in commercial drip systems.
- Hydroponic Systems: Best for DWC and Drip Systems.
Main Pros: Kiln-dried pine shavings are inexpensive and can be found almost anywhere — to include pet stores and feed stores (just make sure they’re additive/chemical free).
Main Cons: Lightweight (not ideal for ebb and flow) and can become waterlogged.
Poly (Polyurethane) Foam Insulation
Foam insulation has indeed been used in hydroponics, but it’s probably not the best growing medium to go with. It retains a little too much water and frankly, it just hasn’t been tested properly (scientifically speaking). Yes, it can probably be used as an alternative to rockwool and oasis cubes, but at the end of the day, that’s not really what it’s made for.
- Medium Characteristics: Spongey foam that has woven air pockets.
- How Commonly Used: Not commonly used in hydroponics.
- Hydroponic Systems: Feel free to experiment with any system but most reports have people using it to start seeds.
Main Pros: Cheap and easy to find.
Main Cons: Hasn’t properly been tested as a growing medium; most reports indicate that it retains too much water. May contain harmful chemicals.
Rice Hulls
Rice hulls aren’t commonly used in hydroponics, but there have been plenty of people who have made them work. Typically mixed in with other mediums, rice hulls are porous, resulting in fairly good aeration and drainage. However, because they’re a byproduct of the rice industry, they may contain unwanted contaminants.
- Medium Characteristics: Small, light-colored casings that resemble sunflower seed shells.
- How Commonly Used: Not commonly used in the hydroponics “hobbyists” community.
- Hydroponic Systems: Drip systems, Wick Systems, and DWC if properly mixed with other growing mediums, and Ebb and Flow/Media Beds if properly mixed with other mediums.
Main Pros: Porous, lightweight, good aeration and drainage.
Main Cons: Difficult to find, may contain unwanted contaminants because it’s a byproduct of rice farming; usually not used as a substrate by itself and has to be mixed in with other growing mediums.
River Rock
River rocks are great for hydroponics and will do well in certain setups. And although they have no wicking capability and won’t hold moisture (because they aren’t porous), that actually makes them ideal for certain systems. Additionally, as they’re extremely easy to find, you should be able to buy them locally or just pick some up from your backyard.
- Medium Characteristics: Round, smooth, irregularly shaped rocks that are formed from tumbling down a river.
- How Commonly Used: One of the most common hydroponic mediums.
- Hydroponic Systems: Great for NFT Systems, DWC, Ebb and Flow, Aeroponics, and Drip Systems. If needing wicking capability — such as drip systems — mix in with other media and place river rocks at the bottom for drainage.
Main Pros: Great aeration due to spaces in between rocks, easy to find, and inexpensive.
Main Cons: Not porous and won’t hold moisture. Usually not used as a standalone medium and is often mixed in with other types.
Rockwool
As one of the most common growing mediums used in hydroponics, rockwool is light, porous, water-retentive, and completely sterile. Created by super-heating granite and/or limestone and melting it down, it eventually gets “spun” into small threads and compressed into different shapes — such as cubes and sheets.
If you’d like a more in-depth assessment of rockwool, read our Rockwool Hydroponics Guide to learn more.
- Medium Characteristics: Stringy, yellowish, and spongy medium that is normally used as insulation.
- How Commonly Used: One of the most common hydroponic mediums.
- Hydroponic Systems: Can be used or mixed in with any hydroponic system. Work great for germinating seeds and cloning.
Main Pros: Sterile, lightweight, water-retentive, drains well, easy to transplant, durable, and reusable.
Main Cons: has a high pH, not biodegradable, and not good for the environment (especially during the production process).
Sand
Sand works well as a hydroponic medium and is fairly common amongst hobbyists. Typically mixed in with other substrates, sand is durable, inexpensive, and readily available for the average grower.
- Medium Characteristics: Several shades and sizes but growers prefer coarse sand as it provides better aeration.
- How Commonly Used: Fairly common in hydroponics.
- Hydroponic Systems: Best for drip systems. Won’t work in systems where it can fall through your net cup(s) or grow area and get into your pump or reservoir (such as an NFT system).
Main Pros: Inexpensive, readily available, can be mixed with other mediums for greater aeration, durable, and reusable.
Main Cons: Not very water-absorbent, possible salt buildup, can get everywhere and foul up your pump, very heavy, can be aggravating to work with, and difficult to clean up/dispose of in certain setups.
Vermiculite
Produced in several different sizes, vermiculite is a great hydroponic medium that is porous, water-retentive, and lightweight. As a micaceous mineral, vermiculite is super-heated until it expands into pebbles. Although it can be used by itself, it’s typically mixed in with other mediums such as coco coir.
- Medium Characteristics: Somewhat resembles pine shavings and hamster bedding. Comes in several different sizes — 0 to 8 mm in diameter — and is lightweight.
- How Commonly Used: A common hydroponic medium.
- Hydroponic Systems: Good for wicking systems, drip systems, and other systems where water retention is important. Great for starting seeds when mixed with other media. Probably wouldn’t do well in an ebb and flow system because of how lightweight it is (would float to the top).
Main Pros: Good wicking capability, porous, water retentive. It also has a high cation-exchange capacity, giving it the ability to hold nutrients for later use.
Main Cons: Is a little too light and can float up the surface in certain setups. It can also become waterlogged, creating ideal conditions for fungal growth and unwanted bacteria.
Water Absorbing Crystals (water-absorbing polymers)
Water absorbing polymers aren’t common in the hydroponics community, but nonetheless, there are many people who have used them and found success. Mainly used in consumer products — such as diapers and cooling rags — they can hold an extraordinary amount of water and can expand 300 times their original size.
- Medium Characteristics: Round or irregularly shaped crystals that come in several different sizes and colors. Better to use a larger size as it allows for more aeration.
- How Commonly Used: Not too common but have been gaining popularity in the gardening and hydroponics community.
- Hydroponic Systems: Great for simple designs. Try soaking the crystals in some nutrient solution, setting them in a container, and then adding in a seedling– such as basil — and that should be all you need.
Main Pros: Inexpensive and completely reusable (can be used over and over again after drying out). Can hold and retain an incredible amount of water.
Main Cons: Smaller crystals may not provide enough aeration and need to be mixed in with other mediums — such as river rock. As they’re not common in the hydroponics community, they haven’t really been fully vetted/tested yet.
Considerations for Mediums in Each Hydroponic System
Aeroponic Mediums
- Aeroponic systems typically don’t use mediums and use a cloning collar instead.
- If using a medium, however, best to use one that’s large and can’t fall through the net cup netting.
- You don’t want a medium that’s water retentive as this will saturate the stem and cause stem rot.
Deep Water Culture (DWC) Mediums
- If transplanting seedlings into a DWC system, use a larger medium that won’t fall through your net cups and won’t hold a lot of moisture.
- If starting seeds in a DWC system, use a medium that won’t fall through your net cups but is also somewhat water retentive. Ideally, you want it to be dry at the top and moist at the bottom.
- Feel free to mix and match mediums until you get it right for your particular setup.
Drip System Mediums
- Use mediums that are water-retentive, have good aeration, and have good draining ability.
- Consider using river rocks at the bottom to help with drainage and prevent pooling.
- Feel free to mix and match with other mediums until you get it right.
Ebb and Flow (Flood and Drain) Mediums
- Can vary depending on your setup, but typically you want to use a medium that won’t “float” up to the top when the media bed is filled.
- Similar to drip systems, consider using river rocks at the bottom to help with drainage and prevent pooling.
- Need to take flood level, drainage, water retention, and good aeration into consideration.
Nutrient Film Technique (NFT) Mediums
- Be careful using a high water-retentive medium around your stems as it might cause stem rot.
- Because you typically transfer seedlings into an NFT system, use a large medium that won’t fall through your net cups and into the system.
- Use hydroponic mediums that are big enough to prevent light from penetrating into your channel or tube (will prevent algae growth).
Wick System Mediums
- Use hydroponic mediums that hold moisture well and are water retentive.