Grow media for hydroponics is a crucial part of the growing process. Without it, there would be nothing to support seedlings as they develop into mature plants, and nothing to protect and stabilize their roots.
What is Grow Media?
Grow media is a hydroponic support system for plants as they develop. They hold seeds during their transition to a hydroponic environment and provide a safe place for plants to spread their roots. Grow media comes in various shapes and sizes, and different materials work better in one system or another.
A good grow media for hydroponics will support your plants, allow them to develop roots easily and access water, while not retaining so much water that it causes plant roots to become waterlogged.
Grow Media Ranked
Grow media is very situational. What works in one system might not work as well in another system. Because of this, the best way to understand the value of each grow media is to analyze them through two ranking systems: a straightforward 1-6 ranking, and then a tiered list.
For this article, here’s how we’re defining each tier:
S Tier:
A superb option. The pinnacle of grow media for hydroponics, works great in every hydroponic system, is easy for beginners to handle or has such striking advantages in a specific system that it makes them impossible to ignore.
A Tier:
Useful in a variety of solutions, but it has a few downsides that prevent it from achieving S tier ranking. Relatively easy for new growers to work with.
B Tier:
A solid option, but the above options are easier to work with. Works well with an experienced grower who can use the grow media to its full potential by minimizing its downsides.
C Tier:
An option that has some benefits, but these benefits are better showcased by another grow media in the higher tiers.
D Tier:
While it can work in very specific situations, grow media in this tier are challenging to get right, and present significant challenges, especially for beginners.
E Tier:
Tricky to use for even expert growers, yet it can be used situationally when required.
F Tier:
Not useful in any situation. You’re better off with another grow media, because the advantages of this grow media are all done better by something else.
With these criteria in mind, let’s see how the following grow media stack up against each other, according to the opinion of our head grower.
Peat/Foam Grow Plugs (Oasis Cubes)
Tier: S
Pros:
- Inexpensive and cost-effective
- Low experience barrier
- Versatile, preferred option for many crops
- Reliable and reusable
- A ‘jack of all trades’ solution for most plants and grow systems.
Cons:
- Over time, water flow will sweep away bits of material, requiring regular upkeep and maintenance.
- Needs to be soaked for an hour before inserting seeds.
Ranking: #1
Grow plugs are a very popular grow media for hydroponic cultivation. In part, it’s due to their stability, as they’re made from sphagnum peat moss and a binder. Because of their unique composition, they can effectively absorb and retain water. Excess water is drained, preventing roots from being waterlogged.
We picked grow plugs as our top grow media because it’s an effective all-around solution with no severe downsides, no matter what you plan on growing. Just make sure to soak them in water before inserting seeds (Check the medium’s usage instructions), and you shouldn’t have to worry about doing anything in addition to your typical hydroponic duties.
Grow plugs work well for crops that have rapid growth cycles, including many of the best crops to grow hydroponically.
Rockwool (Grodan)
Tier: A
Pros:
- Cheap
- Effective
- Consistent
- Inert
- Holds together well
Cons:
- Requires preparation, including soaking material in pH-adjusted water bath.
- The fibers of rockwool can pose health risks if ingested.
- Requires PPE to handle safely, including particle masks to prevent fiber ingestion or inhalation.
Ranking: #2
Rockwool is like a natural cotton candy, just don’t put these thin strand-like fibers into your mouth! Made from molten volcanic rock and limestone, then spun into a fiber, rockwool is an insulating material that was first used with exterior walls, HVAC ducts and roofs before it was discovered to be an excellent grow media.
Also referred to as Grodan to separate it from the same material’s use as an insulator, it was created by Danish scientists in 1969, and was a noticeable improvement over prior sustainable growing systems in that it didn’t have to be disinfected with methyl bromide, a toxic chemical.
Because of its naturally high pH, rockwool must be stabilized before use. When using it, this means that you must make further pH changes to balance out the pH of your nutrient solution. While this can be a challenge, it allows you to customize the media to your plant’s specific pH needs.
Clay Pebbles
Tier: C
Pros:
- Great option for larger plants by giving them more to grab onto.
- Longer grow periods mimic soil-based cultivation.
- Lots of air circulation, reliable drainage
Cons:
- High cost
- Problems with retaining moisture, potentially drying out roots
- Non-degradable
- Requires 48 hours of treatment before it can be used in hydroponics
Ranking: #3
Expanded clay aggregate, also known as clay pebbles, is a grow medium made from clay that’s cooked in a kiln and expanded to five times its size. Compared with other grow media, clay pebbles give the greatest amount of direct air contact due to the decentralized nature of the medium. However, this can be more of a challenge than you might think.
While other grow medias are compact, clay pebbles are spread out. This can be a concern when growing plants that require a firm foundation to root in. Tying stems to the netted pot can provide a little more stability to the system, but some varieties of tall plants may still be difficult to grow.
While clay pebbles can be sanitized after use by boiling them, it’s likely more cost-effective for your operation to purchase new pebbles with each grow season, making them less sustainable than other options on our list.
Coconut Coir
Tier: B
Pros:
- Very consistent
- Improves aeration
- Inexpensive
- Inert
Cons:
- Require netted pots in addition to grow media.
- Coir contains natural salts, which can negatively impact your plant if not washed out
- Needs to be rehydrated before use.
- Can become unstable when used with tall plants
Ranking: #4
Coconut Coir (koi-ER’) is an all-natural fiber that’s taken from the outer husk of mature coconuts. It’s obtained by splitting harvested coconuts in two and is sold in bricks, blocks and chips. Some manufacturers will soften the husk with either a freshwater or saltwater bath.
If you have a choice, always go with husks that have been cleaned with a freshwater bath, as it will have less salt than husks cleaned with saltwater.
When you first get your Coconut Coir, place it in a large container. Your container should be large enough to fit several gallons of water in addition to the expanded coconut coir (It can expand to up to seven times its original size, so plan accordingly!).
Once your coir is fully soaked and saturated, you’ll need to fluff it, just like you would when cooking rice. Put your hands or a spade into the mixture and break it up, ensuring that the entirety of the coir has been drenched.
Coir is an effective, inexpensive grow media for hydroponics that’s popular with many growers because of its combination of excellent moisture retention and root aeration abilities.
Perlite & Vermiculite
Tier: C
Pros:
- Vermiculite is better at retaining water and nutrients
- Ideal for seed starting or plants needing consistent moisture
- Perlite has low to moderate water retention, improving drainage and preventing overwatering
- Great for research use
Cons:
- Asbestos worries
- Challenging for beginners
- Can’t be used with flood-and-flush systems
Ranking: #5
While this grow media is two separate minerals, they’re more effective when used in combination with each other. Vermiculite is commonly added to soil compositions to assist the development of seedlings, with little risk of causing root rot.
On the other hand, perlite retains water, regulating the amount of water plants receive and draining excess moisture from the soil. The two work hand in hand, providing sufficient water and aeration to your plants. These attributes make perlite and vermiculite useful for experienced growers.
However, this combination should not be used without first verifying your grow media’s sourcing. Vermiculite, for much of the 20th century, was mined in Libby, Montana. The mine, closed in 1990, was found to have been contaminated with asbestos.
According to the Environmental Protection Agency, 70% of all vermiculite sold in the United States from 1919 to 1990 was produced at the Libby site. Because of this, it’s important to verify where your vermiculite comes from, and ensure to use vermiculite that isn’t contaminated with asbestos.
Summary
Selecting the right grow media is crucial for achieving success in hydroponic production. As we’ve explored, each type of grow media offers unique advantages and challenges that cater to different growing systems and plant types.
From the versatile and reliable Foam-based growth plugs to the consistent Coconut Coir, understanding the specific needs of your plants and the characteristics of each media can make a significant difference in your hydroponic journey.
Whether you are a beginner or an experienced grower, choosing the appropriate grow media for hydroponics can enhance root development, optimize water usage, and ultimately lead to a bountiful harvest. Not sure what grow medium to pick? Try out foam-based grow plugs first, then experiment with other mediums over time to find which one you prefer.
With this knowledge, you’re well-equipped to make informed decisions and cultivate thriving plants in your hydroponic garden.
Interested in learning more about hydroponics? Contact us today, and we can address your questions and discuss the best systems for your growing needs.
