19 Best Rockwool Alternatives for Hydroponics That You Can’t Miss

Rockwool is the most used growing media for hydroponics. However, in this article we will be focusing on rockwool alternatives for hydroponics, so if you’re interested in that then you should read the entire piece.

As we know, hydroponics is a very clever system that can be set up to grow plants without soil. The growers desired flowers, herbs, fruits, vegetables, etc., are planted in certain types of growing media.

These growing aids are then supplied and exposed to well-balanced nutrient-rich solutions and water, oxygen, light, and heat. The importance of the growing media is paramount. The most common type of growing media is Rockwool.

It is preferred amongst other mediums due to its supremely beneficial sterile structure. It can defend the plant against any outside organisms and/or objects.

Not only that, but it retains a lot more water and holds a higher amount of oxygen compared to its competitors.

Furthermore, Rockwall can hold more heat for longer periods. Rockwool has a few disadvantages, though, making the user turn to rockwool alternatives for hydroponics.

Rockwool alternatives for hydroponics
Rockwool alternatives for hydroponics

Environmental, personal health, and tedious usage, to name a few. Consequently, it’s ideal to look into other growing media to cover all bases. Some other alternatives include coco fiber, vermiculite, perlite, and sawdust, to name a few.

Why is Rockwool Considered as the Industry Standards for Hydroponic Systems?

Rockwool has been the most commonly used growing media within the hydroponics industry for quite some time now. For a good reason also. The way Rockwool is structured allows the roots of the plants to develop with greater strength and freedom than most other media types.

The sterility of the wool offers a much-welcomed shield-like property. The roots can push their way through while being protected from any nasty organisms and other pesky objects that may try to interfere. 

Rockwool can be purchased as cubes in larger slabs and also granulated form. The variation in makeup allows the grower more choice and flexibility with the system they choose to build.

It can also be broken apart and hand-formed to allow more custom type shapes, sizes, and setups. This doesn’t mean that Rockwool is weak, and it is quite durable, and it will only break apart with force.

Why is Rockwool Considered as the Industry Standards for Hydroponic Systems?
Why is Rockwool Considered as the Industry Standards

Rockwool is one of the best media for water retention; it soaks up the water and holds it to the roots, so they rarely dry out. In addition, the amount of water that plants require can be reduced due to this fact. Its aeration capabilities also reign supreme. This characteristic allows the plant’s root system optimal levels of oxygen which encourage stronger growth and stop early wilting.

Another solid feature of Rockwool is its ability to retain its heat. While under light(s), the heat source can sometimes lose its punch with other media. Rockwool can almost suck the heat in and repurpose it as a personal insulator for the plant’s root system. We all know that plants require a certain temperature to sustain optimal growth.

This feat favors the long-term energy bill of growers also. One of its downsides which we’ll go into deeper next, is that it doesn’t come primed with nutrients.

Once the nutrients are administered to the Rockwool, they soak those up along with the water supply, giving the plants every chance to develop to maximum potential. So you could say that one of its downfalls can also be very beneficial.

What are the Shortcomings of Rockwools?

Like most good growing techniques or products, there can also be notable disadvantages. Some hindrances of Rockwool are as follows. 

It needs to be pre-soaked in water before use; otherwise, it’ll suck the nutrient-rich moisture away from your plants. Imagine having a dry sponge and dipping it into a glass of water; the dry sponge will lick all of the water possible. A wet sponge is already wet, and doesn’t need as much to reach full capacity. 

What are the Shortcomings of Rockwools?
What are the Shortcomings of Rockwools?

Additionally, it is durable means that it doesn’t break down so easily. Meaning once discarded, it can be a tough task for the environment to break down. 

Likewise, it can have a negative impact on the health of a human if not used safely. To elaborate, it’s not a good idea to breathe Rockwool in.

In general, anything with particles can get into the lungs and cause unknown and/or unnecessary damage. Identically, it’s not one of the best products to come in direct contact with the skin; it can irritate and should be dealt with using correct personal protective equipment. 

These points could deter the user, but only if they are considered larger issues compared to alternatives. 

19 Rockwool Alternatives for Hydroponics

There are many rockwool alternatives for hydroponics. Some offer a natural approach, and other media types are cheaper or more easily accessible. The personal preference of the grower will ultimately decide the media type. Let’s go through a wide range to learn more about them and their usage. 

19 Rockwool Alternatives
for Hydroponics
19 Rockwool Alternatives for Hydroponics

Coco coir/Coconut fiber

Coco coir is a material or almost a byproduct that comes from coconut husks by a process known as defibering. This fiber is created using steel brushes to comb and remove any ragged or short strands.

Its hydrophilic nature means that it is perfect for the absorption and retention of water. When exposed to water, coco coir forms a sticky, gel-like substance that can help indicate that there is adequate hydration for your plant.

As a result, this indicator helps prevent root rot and fungal issues. Once the substance disappears, it’s time to add more water. You can mix coco coir into your soil mix or use it as a stand-alone growing media. It has been known to contain deposits of phosphorus and potassium.

This means that you will need to adjust your nutrient solution accordingly to avoid applying too much of the one mineral to your plants. Lastly, coco coir is biodegradable.


Perlite is a derivative of mined volcanic glass and has high water content. When exposed to extreme heat, perlite can expand upto 16 times its original volume. Considering this process has already occurred, the result is an extraordinarily lightweight material.

As a result, perlite is an excellent filtration aid due to its almost bubble-like form. It contains tiny cells on its outside that offer great water absorption, which ultimately provides the plant with a stable source of hydration. This also helps regulate the pH level of the plant as it contains a neutral pH level itself.

Another positive aspect of perlite is that it is generally reusable and reasonably inexpensive.


Sand is another natural medium that can be used. As expected, though, its water retention ability and capacity are much less than other types. This will mean that more frequent watering is required.

Additionally, as real sand is generally harvested from bodies of water such as oceans, they contain greater salt content, which can cause higher levels of alkalinity. This grade of sand often requires treatment through acid washing before it can be used effectively.

As sand has a less porous characteristic, its ability to retain water is not as good as other media types. Under these circumstances, and is also less effective in managing and holding nutrients. Sand is best used in drip irrigation hydroponic setups as its granulated form acts as a great filtration system.

Rock Salt

Rock salt can be used with Rockwool or as a stand-alone media. It can regulate the pH levels of the system. (When an excess of limestone is administered, for example).

As a result, it can help swing an acidic level to neutral by being added in small amounts. Rock salt can also act as an antiseptic agent to counteract overgrowing fungus on the Rockwool.

It will ensure that the Rockwool maintains its acoustic characteristic during this assistance process. In general, rock salt contains high amounts of the required minerals that assist hydration. Using the correct amounts of rock salt can encourage healthy and sustainable long-term growth for your plants.

Rockwool Alternatives for Hydroponics
Rockwool Alternatives for Hydroponics

Oasis cubes

Oasis cubes are specifically designed for usage within the hydroponic industry. They are made from natural sources such as perlite, pumice, peat moss, charcoal, etc. The engineered foam cubes are extremely porous, allowing optimal water and airflow.

They are designed using a water-soluble polymer that assists with retaining and releasing important nutrients to your plants. They come in various shapes and sizes, which allow for customization and ultimate versatility.

Oasis cubes are lightweight and simple to maneuver. They are reusable, providing they are not misused and biodegradable for the environmentally conscious.


Sponges may seem like they only have a place in the kitchen or laundry, but their ability to assist water retention also makes them a great asset in the garden. The most common types in hydroponics are the cellulose sponge.

The good thing about these sponges is their capability to hold in those much-needed nutrients and release them when required. They don’t flood the roots with unnecessary amounts of water. Instead, they give the plant access to a steady amount of the required hydration.

They are extremely lightweight, which makes them a breeze to move around. They are also very inexpensive and easy to find a decent supply of. Sponges come in a range of different shapes, sizes, and forms which is great for all growers.

Clay Pebbles

Clay pebbles are like the OG of gardening as well as in hydroponics. They have been used for quite some time and a good reason. They are extremely lightweight and porus, making them a great choice for improved aeration. They have the uncanny ability to capture air and release it to the plants whenever the need arises.

This fact alone essentially assists nutrient delivery right to the plants’ root. Clay pebbles boast a 100% mineral content, making them ideal for accidental undernourished plants. Of course, it’s not possible to rely on the pebbles alone, though.

They are also useful for draining and repotting, and they make even the dullest gardens spring to life with their ornamental charm. Another huge advantage of using clay pebbles is their stability and long-lasting durability. 

Rocks and gravel/Sandstone/Growstone

These media types all offer good air and water retention compared to the more dense options such as perlite and peat. Rocks, gravel, and sandstone are natural products readily available from a range of home depot types stores and gardening supplies.

They can also be created by using a concoction of sand, rock salt, clay balls, perlite, or pumice and vermiculite, which naturally emulate the same products. Growstone, on the other hand, is a substrate made from recycled glass. It is also not too difficult to find a decent supply of but nowhere near as common as the other 3 materials.

These types of media offer good drainage and are supremely durable and sustainable. Lastly, they are easy to work with, and they don’t need to be manipulated to get the required result. 

Rockwool Alternatives for Hydroponics
Rockwool Alternatives for Hydroponics


Vermiculite is another option for use within hydroponics but has a few caveats. It retains water so well that it becomes somewhat waterlogged. As a result, this can cause fungal growth issues and encourage bacteria to latch on and become a pain to remove.

The upside to vermiculite is that it is a natural material. It’s odorless, non-toxic, and doesn’t break down over time. The latter could see it become an environmental issue. There have been cases where it has lasted for at least 2 years.

This is great for those who stick with the product, but the disposal could be a problem again. Vermiculite has also been known to contain small traces of asbestos.

When that word is used, everyone freaks out, and the reaction is warranted. If these types of products aren’t disturbed, they can be a very good product to use. You should always handle them with caution, though. 

Rice hulls

Rice hulls are another great natural option for a grower’s media. They are or were the protective covering of rice grains. They’re lightweight and airy, which is an optimal filtration characteristic. They also help oxygen find its way to a plant’s roots relatively easily.

Rice hulls assist by trapping any excess debris and unwanted particles within the water. This keeps the system unclogged and the water clean. The beauty of rice hulls is that you can never have too much of it, and it will cause problems. If anything, adding extra to your soil can help prevent drying out.

Rice hulls also can keep weeds at bay if blended into the top ½ to 1 inch of soil. One of their biggest issues is that they attract rodents. So be sure to have your system set up out of reach of wandering pests. 


Sawdust is one of the most readily available media that you can find. They sell it almost everywhere, and if they don’t, you can make your own. You need to make sure that it is the right type of wood, though it may not have the desired effect.

Sawdust is great for water retention; it’s lightweight and easy to work with. It is said to be even better when incorporated with suitable amounts of clay, ammonium nitrate, and organic amendments.

One of the issues with sawdust is that the buyer must ensure that the origin has not contained any pathogens or chemicals that could potentially harm their plants. Another minor issue is that it decomposes quite easily.

Sphagnum Peat moss

Sphagnum is completely natural and often overlooked as a hydroponic medium. Its aeration abilities and its great water retention, deem it one of the better mediums that one could use in their system. This product is reasonably cheap and easy to find in gardening supply-type stores.

You would usually buy peat moss as dry compressed blocks and soak them in water for up to an hour before using them. One of its only drawbacks is that it can decompose with excess use, and the particles that break away can block up drip emitters or pumps within the system. Apart from that, peat moss is wonderful to work with!

Rockwool Alternatives for Hydroponics
Rockwool Alternatives for Hydroponics

Polyurethane Grow Slabs

These grow slabs have been around since the dawn of the hydroponics era. Since then, though, they have become outdated by the more commonly used oasis cubes. They can still be used and cheap as well readily available.

Their biggest downfall is the potential toxicity of the material. Coupled with that fact is their inability to be broken down, which can cause havoc on the environment. Polyurethane grows slabs are more suited to assisting seedlings and starting smaller plants.

There are better, more natural alternatives, but they can still do the job as a last resort. One of their greatest assets is their extreme lightweight and versatility.

Jigsaw Foams and Pool Noodles

Jigsaw foam and pool noodles are more of your DIY type of medium. They can be easy to find in toy and pool stores. They are generally lightweight and easily cut to your desired size and shape. Depending on how you repurposing them, you could easily cut in some well-received aeration holes.

As far as water retention is concerned, they wouldn’t offer a great deal. On the plus side, though, they would be able to insulate the plants and protect them from any nasties making their way in.

If they were to get in, though, they would, unfortunately, be stuck in there with the potential of forming their colony! If not maintained, mold could become an issue long-term. 

Gardening/Potting Soil

Gardening soil is a medium that isn’t generally thought about as it goes against the methodology of hydroponics. Nevertheless, some decent-quality soils can be used with great returns. The difference between hydroponic soil and standard gardening soil is how it can release its minerals.

Normal gardening soil offers a slower release, and hydroponics soil releases its minerals faster. As a result, the uptake is faster. Therefore, the growth is also super quick, and the results can be optimized a lot more smoothly.

Due to this fact, plants grown in standard gardening soil will have a lot larger and more robust root systems because they have to fight harder for their minerals.

On the contrary, plants grown using hydroponics have a much smaller and more sensitive root system. Gardening soil used for hydroponics is reasonably inexpensive and easy to find and purchase. It’s light and fluffy and great to work with. It generally does not require any additives or pre-treatments.

Brick shards

Brick shards are similar in form to gravel, made from crushed-up bricks. Brick shards are quite cheap and can be found in most home depot or gardening supplies stores. They are easy to clean; you need to give them a spray. Alternatively, you can empty them into a sieve and rinse them off that way.

They offer great drainage and aeration as they are unexpectedly airey. However, the water can disappear a lot faster, and the roots can dry out if not maintained correctly. Their biggest downfall is that they can change their pH value over time, so they need to be cleaned in a specific manner before reusing them.

Brick shards are also quite heavy, so they may need to be mixed with a lighter medium if required.


Pumice is quite similar to perlite in characteristic and is formed as volcanic rock. It is also one of the best hydroponic growing mediums that you can use for your system. It’s light and porous, which are 2 of the best attributes of a hydroponic medium.

They allow optimal aeration and filtration. They absorb excess moisture, which stops the roots from rotting. As a result, the plant’s roots will grow healthy and strong, ultimately seeing your plants thrive. Providing they are being served in all other areas of requirements, of course! One notable downfall is their inability to retain water due to their large-sized pores.

Lastly, because it is formed from volcanic rock, it can contain levels of sodium considered too high for your plants. As a result, they may need to be leached before use. 

Frequently Asked Questions (FAQs)

Is Rockwool safe to use?

As Rockwool is formed naturally, it is safe to use it as a plant substrate. It is free from any chemicals, and it’s worth using as a hydroponics medium. In contrast, Rockwool has the possibility of posing health issues to human beings.

Especially when coming into contact with the skin and when inhaled. It can cause skin irritation and the eyes and the upper respiratory tract. As a result, breathing difficulties can be succumbed to.

Is rockwool better than Coco coir?

Both mediums have their pros and cons, but coco coir is much better from an environmental standpoint. They both offer high moisture retention and great oxygen availability, and none of the 2 hold nutrients unless treated. So looking at those points, they are level pegged.

In contrast, though, Coco coir has a neutral pH level, and Rockwool is high, meaning using Rockwool will take some leveling out manually. They are both quite durable. Coco will last several seasons before breaking down, and Rockwool won’t decompose at all, so it’s up to the user to decide to go down that path or not.

Ultimately, it’s a battle of budget vs. longevity and or environmentally friendly. As a long-term grower, I’d tend to lean more toward coco coir but thats the hardcore green thumb in me!


As we can see here, Rockwool has some great pros in that it is long-lasting, inexpensive, and it is readily available. The downside is its inability to break down, which is an issue for mother nature. There are also possible health issues that can arise from using this product.

It is a great medium for what it can help a grower achieve. On the contrary, there are a range of good, if not better, products that can assist in optimal growth with your hydroponics system.

Some top picks include the natural coco coir, clay pebbles, and rice hulls. We hope that this has helped you answer some questions and decide on a medium that suits your needs. Thanks for reading!

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