Hydroponic Growing Mediums

Gardeners and farmers use soil as a growing medium to grow the plants that they need.

Soil was considered the only growing substance in traditional gardening or farming systems.

However, after the invention of hydroponics and aquaponics, the concept of using soil as the only growing medium became dated.

Related post: How to Get Started in Hydroponics Gardening

Nowadays, gardeners and indoor farmers are focusing on other media, like coco peat, moss, or minerals, for growing their plants.

On this page:

1. Coco Coir (or Coconut Coir)
2. Peat Moss
3. Rockwool
4. Sawdust
5. Woodchips
6. Pine Bark
7. Rice Hulls
8. Oasis Cubes
9. Vermiculite
10. Perlite
11. Starter Plugs (Rooting Plugs)
12. Pumice
13. LECA or Expanded Clay Pellets
14. Growstones
15. Gravel
16. Sand
17. Brick Shards
18. Polystyrene Packing Peanuts

What is a growing medium?

A growing medium is a material that can be used to grow plants.

These media are alternatives to soil, and we can use them for indoor plants and hydroponic systems.

Growing medium helps the plants by providing moisture and oxygen. In addition, it supports them structurally.

Growing media provides easier access to nutrients because they can retain nutrient-rich water.

Using media like peat moss, coco peat, perlite, or vermiculite can reduce the threat of soil-borne diseases.

As a result, farmers can obtain a better yield, and gardeners can have healthier houseplants.

Choosing the right growing medium for the plants is not so easy. You must know the plant’s preferences.

For example, you can use peat moss as the medium for plants that prefer acidic media.

Before you choose a medium, you must know its properties. This knowledge will help you to choose the right one for your garden.

Qualities of an ideal growing medium

We cannot simply use any solid substances as the media because they may decompose, rise to pathogens, or create an unfavorable environment for the plants’ roots.

An ideal growing medium has certain qualities, which are explained below.

The materials should be inert

An inert substance is not supposed to react with other materials, like air or water.

Reacting with other materials can significantly change the chemical composition, so inert materials are chosen for the growing medium.

The materials should be porous

Better porosity ensures a better-aerated condition, which is favorable for the plants’ roots.

Porous substances help plants to maintain root respiration. As a result, the roots do not rot.

The substances should be soft for the roots

If the growing materials become too hard for the plants’ roots to penetrate, they will not grow and uptake nutrients.

The substances should be soft and porous, ensuring that roots can penetrate properly.

pH Levels should be neutral

The pH of a growing media controls the growth factor because many plants cannot tolerate an acidic environment. As a result, they die prematurely.

Therefore, the pH of the medium should be neutral so that plants can thrive. In addition, the neutral pH range increases the availability of all the essential nutrients.

The substance should expand or shrink under temperature fluctuations

Some materials expand and shrink under temperature fluctuations quickly, while others show this characteristic slowly.

The ideal growing medium does not show a notable change under temperature fluctuations. It can crush the soft roots of the plants.

The materials have a higher cation exchange capacity (CEC)

Growing media should have a good capacity to retain and exchange nutrients.

This characteristic will help the plants to easily uptake the essential nutrients by exchanging them with the materials.

Benefits of using a growing medium in Hydroponics

Using alternative substances for growing plants can be a smart idea as they can be handled easily. 

• It ensures a constant release of the essential nutrients and allows the plants to uptake them. Also, the higher water holding capacity of these materials allows the roots to absorb the water quickly.
• Due to their porous structures, the medium stays oxygenated. Thus, it maintains the respiration process of the roots. Gardeners must use the growing medium to keep the root zone aerated in deep water culture systems.
• Growing media minimize rapid fluctuations in humidity and temperatures, which is very important for plants’ growth.
• The materials used as a grow medium are sterilized, and that’s why they do not contain pathogens.
• Growing medium can give the farmers better control to operate and handle the system. For example, they can easily check the growth rate and conditions of plant roots.

Drawbacks of using a growing media in Hydroponics

The benefits of using these alternatives outnumber the drawbacks. The limitations are very few, but include:

• Though these alternate materials are cheaper, you may either have to sterilize or treat them before using them.
• You may have to spend some money on the initial setup.

Hydroponic: a soil-free system for growing plants

Hydroponic is becoming a more popular growing system day by day, and many people are growing their favorite herbs, microgreens, and crops by installing this system indoors.

Using this method, plants can be grown faster than the conventional system.

In hydroponics, plants are mainly grown in a nutrient-rich solution.

In this process, you have to use a growing medium because exposure of the roots to the water for a longer time can inhibit the respiration process.

That’s why you should search for the right materials to use as your growing media; it’s critical to run your hydroponic project successfully.

Choosing the right growing media for hydroponics?

Hydroponic growers must choose the type of hydroponic growing medium based on the hydroponic systems and plant types.

There are many different hydroponic methods, but there are six popular methods:

• Wick system
• Deep water culture
• Nutrient flow technique (or NFT)
• Ebb and flow
• Drip system
• Aeroponics

For all the designs except aeroponics, you must choose a medium.

In an aeroponic system, water is sprayed on the roots in mist form, and that’s why there is no necessity to use a growing medium in this design.

But you may still use it if you want.

Different growing substances have different characteristics, and they have different demands and provide the best result under certain conditions.

For example, vermiculite and coco peat perform differently due to their water retention capacity.

Although these growing substances are cheaper than other garden equipment, many gardeners become confused with them.

Eventually, they cannot choose the right medium and fail to grow plants.

Here we will take a look at some of the best hydroponic growing mediums for gardeners.

Types of Growing Mediums in Gardening

Coco Coir (or Coconut Coir)

Coconut coir (or simply coco coir or coco peat) is undoubtedly one of the best hydroponic growing mediums because of its multiple benefits.

This substance is extremely easy to get and inexpensive.

You can either make coco coir from the coconut industry or make it from brown coconut husks.

Coco coir is an effective hydroponic media because of its excellent moisture retention and air supplying capacity.

It is an inert substance and does not decompose.

The tiny dust particles can also retain the nutrients for the plant roots to uptake when necessary.

You do not have to worry about root suffocation because this is a porous material.

In addition, coco coir is environmentally friendly and does not contain any pathogens or toxic substances that can inhibit plants’ growth.

You can either use coco coir alone or mix it with perlite, peat moss, or wood chips to create more air pockets.

This medium works better than other media and you can usually buy them as coco bricks.

You can use it in any hydroponics system.

Advantages

• Best water holding capacity
• Better aeration
• Environmentally friendly
• Organic material
• pH neutral
• Better root growth

Disadvantages

• Initially, it needs to be treated by water to remove excess salts

Related posts: Peat Moss vs Coco Coir: Which Growing Medium is Better?

Peat Moss

Peat moss is the second-best hydroponic growing medium that is widely used.

This dead fibrous material can be found in cold, wet, and acidic areas, also known as bogs.

In these anaerobic environments, moss and other organisms decompose into a dark-colored substance known as peat moss.

It takes around a few thousand years to form this material.

These growing media have the highest water retention capacity. They are soft and durable materials.

You can either use it alone as the hydroponic media or mix it with other lightweight materials. It does not compact easily after rewetting.

However, peat moss is a nonrenewable material, which can be a drawback for using this.

To use it as a hydroponic growing medium, you can mix it with other porous substances like perlite, wood chips, or expanded clay pebbles.

Advantages

• Highest water holding capacity
• Good cation exchange capacity
• No harmful microorganisms

Disadvantages

• Acidic
• Expensive and nonrenewable

You can use it for all hydroponics systems, but problems may arise because of its low pH.

Rockwool

Rockwool is another fascinating growing medium that beginners have widely used in recent years.

It can absorb too much moisture, but plants can uptake water when it is necessary.

Rockwool can be an effective medium for your hydroponic setup.

If you are a commercial hydroponic gardener, we recommend using this material as the growing medium.

There is another material like Rockwool, and it is oasis cubes.

Rockwool is porous and has a high water retention capacity. As a result, gardeners do not have to worry about the irrigation cycles.

This substance is made up of heated limestone or granite rocks.

People may get manifold benefits by using Rockwool as the growing medium in hydroponic setups.

It can protect the plants from becoming dehydrated, and at the same time, the plant roots will get plenty of oxygen for respiration.

Advantages

• Good water retention capacity
• Good aeration
• Easy to maintain

Disadvantages

• Not friendly to the environment
• The pH level of the nutrient solution may change

Best hydroponics system for rockwool As a Growing Medium

• Flood and drain system
• NFT
• Drip system

Since these materials retain too much moisture, it is better not to use them in a wick or deep water system.

Sawdust

You can find this amazing material in every sawmill. Sawmills produce sawdust as a by-product of their manufacturing processes.

It is inexpensive and a popular choice among hydroponic farmers.

These are organic materials that are extremely light and can retain water for a longer period.

Sawdust is rich in lignin, and that’s why you do not have to worry about its decomposition process.

Sawdust decomposes over time, but the rate is quite slow. That’s why the pH may slowly decrease.

Therefore, you may need to monitor the pH fluctuations and take extra care of them.

One more thing, you must know the plant species of the sawdust because the chemical composition, pH, and other properties may vary from plant to plant.

Sawdust medium performs better than river sand or vermiculite [1].

Advantages

• Organic
• Good water retention capacity
• Sustainable

Disadvantages

• pH fluctuations
• Decompose over time
• Sterilization is needed

Woodchips

Woodchips are similar to sawdust, but these materials are coarser and more porous. They can be a great option for deepwater systems.

These substances are eco-friendly and popular among gardeners.

However, you must know the species of the plants before using woodchips. Some woodchips may contain pathogens or contaminants.

This is why these materials need to be sterilized properly before using as hydroponic growing media.

This material can retain water well, but the problem arises in flooding and draining systems.

You can use it with organic compost to enhance the efficacy.

Lastly, you can use sawdust for any hydroponics system (with the exception of flow and ebb systems). With that said, these are the hydroponic systems that are best suited for woodchips.

• Wick system
• Deep water
• Nutrient film technique systems

Advantages

• Organic material
• Porous
• Inexpensive

Disadvantages

• Biodegradable
• Contain chemicals or pathogens

Pine Bark

Pine bark is an amazing organic material that can help you make a porous medium for the hydroponic setup.

You may find three kinds of pine bark: aged pine bark, fresh pine bark, or composted one. As a hydroponic substrate, you may mix all of them.

Due to its cellular composition and lignin content, pinewood is resistant to rapid decomposition.

As a result, it produces fewer acids that can acidify the solution.

The nutrient content varies based on the stages of the bark. For instance, fresh bark lacks nitrogen, while aged pine contains more nitrogen.

You can avoid this issue by adding composted pine bark to the medium.

Best of all, you can use pine bark safely as it’s great for any type of hydroponic setup.

Advantages

• High porosity
• Excellent water holding capacity
• Add nitrogen to the solution

Disadvantages

• Woods may contain harmful chemicals if it is manufactured.

Rice Hulls

Rice hulls are the by-products of rice, and you will find these materials in any rice mill.

They can be an excellent addition to potting soil mixes or hydroponic growing media.

During the manufacturing process, the mills produce a lot of rice hulls.

The pH of this substance ranges between 6 to 7, indicating a neutral level.

However, you must remember that rice hulls are not sterilized, and that’s why they may contain pathogens.

Therefore, using parboiled rice hulls is a better choice as they are clean and dried.

They are porous materials and have a good drainage system.

It ensures that your plants will receive abundant oxygen to maintain their respiration processes.

Rice hulls can be used on any hydroponics setup.

Advantages

• Organic
• Extremely lightweight
• Porous material

Disadvantages

• May not be sterilized
• pH may fluctuate
• Decompose over time

Oasis Cubes

Oasis cubes have different names. They are also known as grow cubes, germination cubes, or floral foam. You can use them for starting seeds.

The characteristics of these cubes are similar to Rockwool.

This inexpensive medium can retain water very well. Also, you do not have to worry about pH fluctuations.

Due to the presence of capillary pores, the root zone can stay aerated for a longer period.

However, this floral foam does not have a cation exchange capacity.

So, they will not retain nutrients for your plants, but still, your plants can uptake nutrients from the solution.

Advantages

• Best medium for seed germination or plant propagation
• Neutral pH
• Higher water retention
• Reuseable

Disadvantages

• Not environmentally friendly
• Initial setup cost can be higher

Best hydroponic setup for Oasis Cubes

• Flood and drain system
• NFT system
• Drip hydroponics

Vermiculite

Vermiculite is a type of hydrated mineral that expands due to extreme heat.

Due to its higher water retention capacity, hydroponic growers use this material as the hydroponic growing medium.

They are like clean and odorless small pellets and a great choice to use as hydroponic growing media.

Vermiculite is a non-toxic, moist-resistant, and sterile substance used for any soilless planting media.

It is lightweight like perlite, but vermiculite has better moisture holding capacity with poor aeration.

The pH of this material is neutral, and its CEC is high enough to retain essential nutrients.

Due to its unique properties, it is better to avoid using it in deep water hydroponic systems because root suffocation can be dangerous.

Advantages

• Higher moisture holding capacity
• High cation exchange capacity
• Lightweight
• Inexpensive

Disadvantages

• Drainage capacity is poor

Best hydroponic growing system for vermiculite

• Ebb and flow systems
• Nutrient film techniques
• Drip systems

It is better to avoid using vermiculite in wick systems

Perlite

Perlite is a very popular hydroponic growing media because of its availability and higher porosity.

Traditional gardeners use these materials in their gardens to make the soil more porous and well-structured.

Perlite is a type of volcanic glass-forming under intense heat. It is a lightweight material and a good choice for hydroponic gardeners.

Due to its higher porosity, it can be an excellent growing medium for the wick system.

In terms of pH, perlite is considered neutral, which means you can easily use it to grow a wide range of plants.

This material is often mixed with vermiculite or coconut coir to enhance the water retention capacity of the media.

Advantages

• Inexpensive
• Lightweight
• Reusable
• Air retention capacity is high

Disadvantages

• Dust can be deadly.
• Water retention capacity is lower than other substances.

Best hydroponic system for perlite

• Wick system
• Deepwater culture
• Drip system
• Try not to use it in ebb and flow, nutrient film technique, or aeroponics system.

Related post: Perlite vs Vermiculite: Which is Better to Use in Hydroponics?

Starter Plugs (Rooting Plugs)

A relatively new hydroponic and indoor-growing media is effectively a sponge-like polymer-based growing medium.

Seasoned growers call them starter plugs, plant starters, or rooting plugs, as you can readily germinate your seeds in these ‘plugs.’

Starter plugs are made by binding a growing medium (mostly soil) with plant-derived polymers, so they don’t fall apart.

Each starter plug is infused with nutrients and provides a unique matrix for the optimal air-to-water ratio resulting in explosive early root growth.

So how do you use these starter plugs? Simply place a couple of seeds in each plug and store them in a dark place for a few days.

Once your seeds have sprouted into seedlings, take them to a bright area to get some light.

Keep adding water to the bottom of the tray to allow roots to form and strengthen.

Advantages

• Great for germinating seeds
• Sustainable
• Small and compact

Disadvantages

• Only good for cloning plants or starting seeds
• Relatively expensive

Tips on Using Starter Plugs

When you first open the pack of starter plugs, check for mold or mildew. Also, look for any white layer on the top.

If you notice any of this, this means there is mildew growth. Discard the plug if it shows any sign of unusual growth.

More detailed post: Rapid Rooter Plugs To Germinate Weed Seedlings?

Pumice

Pumice is a popular hydroponic growing medium that is formed from volcanic rock.

It is similar to perlite, and depending on the location of the mineral, the color varies. The most common colors of pumice are white, yellow, or pale gray.

You can differentiate it from perlite by observing the color. The color of perlite is lighter than pumice.

This material is lightweight and porous. As a result, it has a good aeration capacity but less water holding capacity than vermiculite.

Many hydroponic farmers use pumice in their systems because it is easy to get and provides excellent aeration to the medium.

Advantages

• Good aeration
• Lightweight
• Easy to handle

Disadvantages

• Cannot be used in flow and ebb system.

Best hydroponic system for pumice

• Wick system
• Deep water system
• Drip
• NFT system

Related post: Pumice vs. Perlite: When Do You Use Them?

LECA or Expanded Clay Pellets

Expanded clay pellets are also known as LECA or hydroton. LECA means lightweight expanded clay aggregate and is like small and rounded balls.

They can provide sufficient air space to the hydroponic media, ensuring a better drainage system.

These substances are lightweight due to their high porosity, but still, they can give your plants solid support to stand upright in the system.

Expanded clay pellets ensure a great balance between oxygen and water in the solution.

You can sterilize and clean the clay pebbles before using them as the media.

However, like other minerals, like perlite and vermiculite, these lightweight clay pebbles do not have a great water holding capacity, but their porous structure can prevent root rotting.

To enhance the water retention capacity of these clay pellets, you can mix them with coconut coir, coconut fiber, or vermiculite.

Advantages

• Sustainable
• Good drainage
• pH neutral

Disadvantages

• Poor water holding capacity
• Expensive

Best hydroponic setups for LECA

• Wick
• Deep Water system
• NFT
• Drip

Do not use it in flood and drain systems.

Growstones

Growstone can be a great medium for a hydroponic garden. The pore size of this medium is larger. As a result, it can provide better drainage.

Thus, growstones can ensure a stable and better-drained system for the setup.

They are non-compacting and non-clogging materials that facilitate root growth. Roots can absorb water and dissolved nutrients present in the solution.

These substrates are similar to lightweight pebbles with higher total porosity.

Besides, growstones are sustainable and do not cause harm to the environment. However, the problem arises while reusing the material.

Plant roots may stick to the medium after harvesting.

Advantages

• Lightweight
• Sustainable
• Cheap
• Good air to water ratio

Disadvantages

• Cleaning can be hard

Best hydroponic setup for growstones

• Wick system
• Deep water system

Gravel

Gravel is a popular and inexpensive medium for hydroponic culture. It can be found is almost everywhere.

They are like coarse rocks, and that’s why the space between the particles is quite large. It ensures maximum exposure to the air.

Sufficient air accessibility in hydroponic culture can prevent both root and stem rot.

But due to their poor water holding capacity, you must maintain the flow system of the nutrient solution.

However, these materials can be reused, and there is no risk of pathogens.

If you can prepare the nutrient solutions properly, this medium can enhance plant health by supplying macro and micronutrients.

Advantages

• Inexpensive
• Durable
• Good drainage

Disadvantages

• Poor moisture retention capacity

Do not use it in flood and drain hydroponic culture.

Sand

Sand is a popular hydroponic grow medium, and you can find it almost anywhere.

In many areas and hydroponic farms, sand is used as the main medium for hydroponic media.

Sand particles are like tiny rocks. The characteristics are the same, but these materials can hold water for a longer period than larger rocks do.

However, due to its small size and porosity, this medium can be compacted within a short period.

This cheap and available material can be mixed with other minerals like perlite or vermiculite to increase efficacy.

Before using sand as the hydroponic grow medium, ensure that it is sterilized and does not contain any pathogens.

Advantages

• Cheap
• Available

Disadvantages

• Can be compacted
• Dries out quickly
• May clog the system

Best hydroponic culture

• Wick system
• Deep water system
• Drip culture

It is better not to use sand as the medium in NFT, aeroponics, and flood-drain systems.

Brick Shards

Brick shards are not much popular hydroponic medium, but you may use them as a beginner.

These are crushed-up bricks, and you will find them in different shapes and sizes.

As a hydroponic medium, these materials can increase the number of large pores. As a result, the medium will not be able to hold moisture for a longer duration.

Also, there is much possibility that pH may fluctuate. 

Sometimes, the growers will have to be careful about the cleaning because the dust may cause clogging of the pores.

Advantages

• Inexpensive
• Good drainage system

Disadvantages

• Cleaning is necessary
• Affects pH
• Dries out very fast

Best hydroponic culture for brick shards

• Wick system
• Deep water system

Polystyrene Packing Peanuts

Polystyrene packing peanuts can be found in shipping industries. These materials are cheap, and you can find them very easily. 

These substances are lightweight and drain very well. Since it contains polystyrene, it is better not to mix them with garden soil.

You should always use these polystyrene packing peanuts as the lone medium.

However, there is a possibility that the plants may absorb styrene chemicals, which indeed pose the risk of contamination.

Advantages

• Inexpensive (free often)
• Lightweight
• Drains out quickly

Disadvantages

• Plants may absorb styrene chemical

Best hydroponic setup for polystyrene packing peanuts

• NFT

FAQs

Conclusion

Hydroponics is a soilless growing culture, where the gardener can plant either his favorite herbs or other crops.

A vertical hydroponic setup can enhance the beauty of your garden.

Plants grown using a hydroponic method can be healthy if you can create a balanced nutrient solution.

Also, due to the availability of water, the plants will look fresh and greenish.

In this culture, you need to choose the growing mediums, which play a critical role in the root system.

Porous hydroponic media can ensure good oxygen to water ratio.

As a result, plants can carry on their root respiration process, and at the same time, they can uptake water and other nutrients from the nutrient solution.

References

• [1] Wahome, P.K.; Oseni, T.; Masarirambi, M. and Shongwe, V.D. 2011. Effects of Different Hydroponics Systems and Growing Media on the Vegetative Growth, Yield and Cut Flower Quality of Gypsophila (Gypsophila paniculata L.). World Journal of Agricultural Sciences, 7(6): 692-698.
• De Brabandere, S. 2020. Hydroponics: Gardening Without Soil. Retreived from website: https://www.sciencebuddies.org/
• Lagomarsino, V. 2019. Hydroponics: The power of water to grow food. Retreived from website: https://sitn.hms.harvard.edu/
• Shrestha, A.; Dunn, B. 2017. Hydroponics. Retreived from website: https://extension.okstate.edu/
• Growing Hydroponically: Growing Media. Retreived from website: https://cals.arizona.edu/