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Hydroponic Media

Hydroponic Media

Although growing hydroponically is soil-free, this doesn’t mean that there is nothing to support our plants.  In most hydroponic systems, growers use different types of hydroponic media to help support their roots and maintain a good water/oxygen ratio.  In this guide, I’ll give you a breakdown of the most popular types of hydroponic growing media.  Every hydroponic gardener has their own preferences, so I’ll give you the advantages and disadvantages of each medium so you can choose the one that works right for your situation.


Types of Hydroponic Media


Coco Peat / Coco Coir

Hydroponic Growing Media Coco Coir

What is it

Coco coir is quickly becoming a favorite among hydroponic gardeners.  It’s made from ground up coconut husks and represents a giant leap in hydroponic growing media.

To understand why ground coconut husks are becoming so popular, let’s take a look at what a coconut husk does for a coconut.  Coconuts are grown in tropical regions, and often times they fall into the ocean when they are ripe.  The husk protects the seed and flesh from sun and salt damage.  Most importantly, the husk acts as a great growing medium for the coconut to germinate and create new trees.

Now apply these benefits to hydroponics.  The ground up coco coir will act as a great hormone rich and fungus free medium for our plants.  In the same way that it helps the coconut to germinate, it will help all of our seeds and seedlings to start strong.  Coco coir has a great air to water ratio, so we don’t have to worry about drowning our roots.  Best of all, it’s completely renewable.  Coconut husks would generally go to waste or be composted if they weren’t used in hydroponic applications.  Here, we’re taking what was once a waste product and re-purposing it to grow more plants!

Growing Tips

When coupled with fabric pots moisture problems can be avoided.

Built up salts can often be a problem, but there are many lines made particularly for coco that allow for easier flushing. Try using Canna Coco and Smart Pots.

Benefits

  • Usually organic
  • Sustainable
  • Compactable (buy compressed, expand at home…saves money on shipping)

Downsides

  • Holds a lot of water and may drown plants

Where to Buy

Expanded Clay Pellets

Hydroponics Growing Media Hydroton

What is it

Arguably one of the most popular media to use in days past has been hydroton expanded clay pellets.  As their name suggests, these are made by expanding clay to form round balls of porous material.  The best part about them is the fact that they release almost no nutrients into the water stream and are pH neutral.  In addition, their spherical shape and porousness help to ensure a good oxygen/water balance so as not to overly dry or drown the roots.

In my experience, the only two downsides to using hydroton pellets has been their weight and their draining ability.  In certain hydroponic systems, like ebb and flow, filling up an entire flood table full of hydroton is going to leave you with a very heavy system.  They also drain and dry out very fast because there is much more space between each pellet than other hydroponic growing media.  They can be used to great effect to line the bottom of an growing tray, when draining is an issue.  Other than these two disadvantages, hydroton pellets are a great, re-usable media to use!

Benefits

  • Reusable
  • pH neutral
  • Does not compact

Downsides

  • Heavy
  • Drain and dry very fast, roots may dry out
  • Harder to find
  • Strip mined (environmental concerns)

Reader Experiences

Endlessly reusable, but heavy and drain kind of poorly – can dry out roots.

Works great as a reusable medium and allows for easy plant and root removal. Roots sometimes get entangled in the pellets but generally they are easily cleaned.

Where to Buy

Sure To Grow

Hydroponic Growing Media Sure to Grow

Sure to Grow is the leading company offering a plastic-based growing media.  There are two camps here: one side loves STG, and the other can’t stand it.  STG’s marketing suggests that it’s a wonderful growing media that has a plethora of advantages over other growing media, but the gardening community seems to be on the other side of the coin.

Reader Feedback

Just don’t really like this, I feel like they re branded a basic plastic medium as some magic media.

In the industry we call this stuff “sure-not-to-grow” because it sucks. Spun cotton breeds algae and makes me really mad.

 I currently use it in Ebb & Flow and my experience with it at first was generally negative. Once my plants got older I started to see the benefits of it and now for long term grows, I actually prefer it to most other medium.

Benefits

Roots embed deeply into the medium and the plants and medium become one.

Downsides

Expensive, not re-usable, Need to have a top layer that stays 100% dry or it promotes algae growth.

Where to Buy

Oasis Cubes

Hydroponic Growing Media Oasis Cubes

What Is It

Oasis Cubes are similar to rockwool cubes.  If you’ve ever gotten flowers in that strange green foam-like substance, then you have a good idea what oasis cubes are like.  It’s an inexpensive media that you can use for the germination and seedling grow phases.

Reader Experiences

I absolutely LOVE the new oasis cubes. They reformulated their blocks a couple of months ago and the new stuff ROCKS. It no longer “crumbles” but crushes instead.

It is an inert media like rockwool but a fraction of the price. From the first couple of trials we have seen no germination or growth difference in comparison to rockwool and it comes in dozens of different shapes and sizes, and requires no presoaking.

Benefits

  • Inexpensive
  • No presoaking

Downsides

  • Not sustainable
  • Not organic
  • Useful for germination only, not as a full growing medium

Where to Buy

  • Any gardening / hydroponics outlet

Perlite

Hydroponic Growing Media Perlite

What is it

Perlite is something that many traditional soil gardeners already recognize.  It’s a soil-free growing medium that has helped to add aeration to soil mixes for years.  It’s created by air-puffing volcanic glass to create an extremely light and porous material.  It has one of the best oxygen retention levels of all growing media because of how porous it is.

Its weight can be a downside in certain hydroponic systems where water interacts directly with the growing media, causing it to shift around and wash away.  Because of this, perlite is rarely ever used alone – typically it is mixed with coco coir, soil, or vermiculite.

Benefits

  • Lightweight
  • High oxygen retention level

Downsides

  • Too lightweight for certain hydroponic systems
  • Strip mined (environmental concerns)
  • Potential particle inhalation danger

Growing Tips

Straight perlite growing is one of the tried and true methods of hydroponic production. With virtually no cation exchange this media is a great option for longer term crops; especially in drain-to-waste scenarios. You have to watch out for moisture deficiencies as it holds absolutely no water!

Where to Buy

Starter Plugs

Hydroponics Growing Media Rapid Rooter ®

What is it

A new and innovative entry into the hydroponic media space is what I will call a sponge start.  It’s made up of organic compost and doesn’t break apart like soil due to a biodegradable binding material.  Pictured above is a Rapid Rooter ® starter plug that I have planted a Blue Dwarf Kale plant in.

For those who are concerned about sustainability and organics, sponge starts are a great way to start seeds and incorporate them into your hydroponics system.  I use these extensively for my seedlings and clones and I have to say that they are the most convenient and simple way to start out large quantities of new plants.  You simply place them in trays and the roots grow straight downward towards the opening in the tray at the bottom.  This is helpful when transplanting into any type of hydroponic system, where roots growing out to the sides aren’t as beneficial.

Benefits

  • Compact
  • Great for starting seeds
  • Relatively sustainable

Downsides

  • Only suitable for starting seeds or cloning
  • Expensive

Growing Tips

If they remain wet and fungus gnats are a problem in your area, the gnats will infect the plugs.

Where to Buy

Rockwool

Hydroponic Growing Media Rockwool

What is it

Rockwool has been around for decades and is well-known in the hydroponic growing community.  It is made by melting rock and spinning it into extremely thin and long fibers, similar to fiberglass.  They take these fibers and press them into cubes of varying sizes.

Rockwool has all of the benefits of most growing media, with some pretty serious downsides.  It’s not easy to dispose of – thin fibers of melted rock will last essentially forever when disposed of.  Additionally, they usually come at a high pH and need soaking.  The fibers and dust created in the spinning and compressing process can be harmful to eyes, nose and lungs.  You can prevent the dust by immediately soaking rockwool in water once you take it out of the package.  Because of these downsides, rockwool is rapidly being replaced by starter plugs as a reliable way to get seeds sprouting in your garden.

Benefits

  • Great water retention
  • Easy to dispose of

Downsides

Where to Buy

Growstone

Hydroponic Media - Growstones

What is it

I came across growstones a while back at a hydroponic expo and fell in love.  The company takes discarded glass bottles from landfills, crushes them into a powder, melts the powder, and mixes in some calcium carbonate.  It bubbles and then they cool the mixture and break it up to form what looks like lava rocks.

It’s extremely lightweight, sustainable, and a great medium in almost any application.  The one downside I”ve run into is that you typically can’t reuse it because roots will stick to it after harvest and ruin sterility.

Benefits

  • Lightweight
  • Great air to water ratio
  • Sustainable

Downsides

  • Hard to clean

Reader Experiences

Cheap and easy to use. One disadvantage is that due to their irregular sizes is that you have to mound more of them up to prevent light from entering your reservoir.  Also if you tend to move plants from one medium or grow area to another as they get larger (like I do), Growstones tend to grip the plant roots too much and cause root damage. For this reason they are best used in a permanent grow bed.

Where to Buy

Rice Hulls

Hydroponic Media - Rice Hulls

What is it

These are the shells that surround rice. They allow for good drainage and retain little water in general. Rice hulls are a product that would normally be thrown away, so putting them to extra use in hydroponics re-purposes something that would otherwise be thrown away.

Benefits

  • Makes use of a byproduct that would otherwise be wasted
  • Retains little water

Downsides

  • Decays over time

Where to Buy

Pumice

Hydroponic Media - Pumice

What is it

Very similar to perlite.  Lightweight mineral that is crushed and used in some hydroponics systems.

Benefits

  • Lightweight
  • High oxygen retention level

Downsides

  • Too lightweight for some hydroponic systems if bought as small pieces

Where to Buy

Sand

Hydroponic Media - Sand

What is it

One of the most plentiful types of media on the planet!  Sand is extremely cheap (or free!) Sand is cheap and easily available. It’s a great way to get started, but it is fairly heavy, must be sterilized often, and has low water retention. Arguably the oldest hydroponic media, holds no water or nutrient load and can exacerbate deficiencies quickly.

Benefits

  • Cheap
  • Easy to find

Downsides

  • Heavy
  • Low water retention
  • Small size may affect certain hydroponic systems

Where to Buy

Gravel

Hydroponic Media - Gravel

What is it

This is the same material that is used in aquariums.  As long as it is washed, you can use any type of gravel. Relatively cheap and easy to clean.  A great DIY starter media if you’re short on cash!

Benefits

  • Very inexpensive
  • Easy to clean
  • Drains well

Downsides

  • Heavy
  • Plant roots may dry out
  • Not suitable for certain hydroponic systems

Growing Tips

Works very well as long as it is not in contact with the water or it can cause PH swings. Great medium because it is cheap and readily available. It can be reused but due to their small size, it is common that they get very tangled in the plant roots which makes it not worth removing and cleaning since it is already so cheap.

Where to Buy

Wood Fiber

Hydroponic Media - Wood Fiber

What is it

Simply wood.  Great and efficient media for hydroponics.  If you want to go truly organic with your growing media…you can’t get any better than wood chips!  Additionally, some studies have indicated that wood chips reduce the effect of plant growth regulators, meaning your plants may grow slightly larger.

Benefits

  • Organic
  • Holds structure for a long time

Downsides

  • Biodegradable
  • May not be sterile
  • May attract pests

Where to Buy

  • Local home improvement store
  • Garden center

Brick Shards

Hydroponic Media - Brick Shards

What is it

Name says it all: crushed up bricks.  Very similar in effect to gravel.  However, they may affect the pH as they are not pH neutral, and also require extra cleaning to get rid of brick dust.

Benefits

  • Inexpensive
  • Easy to clean
  • Drains well

Downsides

  • May affect pH
  • Requires more thorough cleaning
  • Heavy
  • Plant roots may dry out

Where to Buy

  • Local home improvement store
  • Garden center

Polystyrene Packing Peanuts

Hydroponic Media - Polystyrene Packing Peanuts

What is it

These are the standard packing peanuts used in the shipping industry.  They’re cheap, available everywhere, and drain fairly well.  Tough to use uncovered outdoor due to their light weight…the typical use is in Nutrient Film Technique systems.  There is the possibility that plants will absorb styrene, so these may pose a contamination risk.

Benefits

  • Cheap (often free)
  • Very lightweight
  • Drain well

Downsides

  • Only polystyrene will work – biodegradable packing peanuts will turn to slush
  • Potential for plants to absorb styrene

Where to Buy

Vermiculite

Hydroponic Media - Vermiculite

What is it

Vermiculite very similar to Perlite.  It’s a mineral that is heated until it expands into pebbles. It retains more water than perlite and can wick (draw) water and nutrients upwards.  Often used in combination with other types of media to create a highly customized media for specific hydroponic applications.

Benefits

  • Water retention

Downsides

  • Hard to find
  • Expensive
  • Can hold too much water

Reader Experiences

Dirty nasty stuff that clogs up feed lines in recirculating systems, but is particularly useful in large scale drain-to-waste operations that need an increased cation exchange.

Where to Buy

Which Should You Choose?

With all these choices, it’s hard to make a decision as a beginning hydroponic gardener, isn’t it?  No need to fret – I’ll do the analysis for you!  Click here to download my Hydroponic Media Spreadsheet so you can make the best choice based on your particular needs.  Dont worry – it’s completely free!

*Spreadsheet coming soon!

About Kevin

Kevin is the creator of Epic Gardening, a community dedicated to teaching urban gardening, hydroponics, and aquaponics. He enjoys skateboarding, piano, guitar, business, and experimenting with all kinds of gardening techniques!

35 comments

  1. How do you think marbles would workout? They could act like the clay balls, but are a neutral glass. I ask because I’ve had a hard time finding other things.

    • I’ve given marbles some thought, but I think you would run into problems. The hydroton expanded clay pellets hold moisture pretty well, where the glass marbles wouldn’t hold any at all. Depending on what type of system you were running you would have to be very sure that the roots weren’t getting too dry. If you’re having a tough time finding something, you can use gravel, which you should be able to get at an aquarium store. More surface area, smaller pellets and a more granular surface will help the water stay around longer and give your roots the moisture they need.

      • I’m doing a deep water system for now, so the roots should be submerged. With that being said, is water retention something to be concerned about? There is no hydroponics store around (that I know of) and garden supplies at the big box stores are limited right now. I have seen vermiculite. I’m using plastic pots with the holes drilled in them, so I worry about the pellets falling out.

        • Water retention matters until the roots hit the water – after that they’re just sitting in a nice oxygenated bath of nutrients, but before that point they’re vulnerable to drying out. Extra coarse vermiculite could definitely work. How big are the holes that you drilled?

        • Lava Rocks baby. I have seen people use them with some degree of success, and they are usually big enough to not fall through your holes. Really though, order some hydroton on amazon or something, it’s what will do you the best in the long run and it’s reusable.

          • My personal favorite media and not lava rocks: Growstones. They look exactly like lava rocks, but are really made from recycled crushed glass (factory set up near landfills), baked until bubbles form and cooled, then broken into rock like shapes. They’re totally awesome and I met the salesman/friend of the founder at a hydro convention recently!

    • I would NOT use marbles. Like Kevin said, they don’t hold any water or air, which is half the purpose of Hydroton. You really need that moisture and oxygen, at least until the plants grow some good rots and get down into your reservoir. Plus it is re-usable so it’s one of the more environmental friendly growth mediums.

    • marbales would not work because thay dont absorbe water

    • Maybe you can try using marbles with Super absorbent polymers(SAP) that you can get from disposable diapers.

  2. Awesome guide! Thanks for taking the time to write this up.

  3. Hei Kevin,
    First of all congratulations for your website. Very good.
    Im doing a small aquaponic system and Im using expanded clay. But to grow the seed I dont wanna use the rockwool. I want to use something organic. Do you think this Starter Plugs could be an option? If not do you know other possibilities.
    It is a close system. The water goes from the fish tank that is pumped to the growing media.
    Thanks a lot
    Lumiar

    • Hi Lumiar,

      Thanks for the compliment, glad it’s been helpful to you.

      Starter plugs would be a great solution in this case – made from organic peat moss and some bioadhesive. They’re easy to transplant into expanded clay as well. I would recommend, these starter plugs as I have used many bags of them and love the results. Let me know if you have any other questions!

      Kevin

      • What about water-beads (or hydro-beads, crystal beads, water pearls etc.) Have you thought about them? They can absorb nutrients, and release them over time. I am thinking of starting my first hydroponic system, and have also recently pre-ordered an Aqua-Farm from Back to the Roots. But again, my concern lies with the media. I recently purchased 2 lbs of clay stones, but those will not be enough but to do a few containers. I do have an Avocado seed, as well as a bean seed (both growing in water-beads)that have been doing rather well for about 5-6 weeks now. No root rot or discoloration yet. I do have the containers light proofed, as to discourage algae or other growth. Any help would be appreciated.
        PS – I really want to do a window farm, but am not sure what to use as media…HELP!!!

        • Hey Kayla,

          Thanks for the comment! I personally wouldn’t use the hydro beads because of the fact that they absorb the nutrients and release over time. I prefer the plant’s roots to take what they need out of the water itself instead of relying on the medium to transport the nutrients. However, you can always experiment…they could turn out to be awesome! One more thing: I’m not sure how well they keep pH stable.

          I REALLY like GrowStone as a media, which you can buy here. Made from recycled glass, great air:water ratio, and reusable (to a point). The factories are very sustainably built and operated as well. Hope that helps!

          Let me know if you have any other questions :)

  4. i was wondering if u put together the spread sheet on medium mixing?

  5. Hi, the section “Sheep Wool” got lost, the link in the index is dead

  6. Thanks for the information…its very helpful.

    Joey

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