Hydroponic growing may not involve any soil, but you still need to use a medium to support the plant roots. Hydroponic media also helps develop seedlings and provides a mixture of conditions for proper growth with enough oxygen and nutrient water.
There are also various types of hydroponic growing medium you can use, and they all come with different benefits for your system. So, join us as we dig deep into the best growing medium for hydroponics and its use with advice on which medium to use!
The Purpose Of Hydroponic Growing Media
There are several reasons why nearly every hydroponic system needs growing media to entice plant growth. First off, hydroponic media provides moisture retention which is important for the initial stage of growth once you plant a seed.
Also, it provides the much-needed stability for the plants to grow and spread their roots. Growing media acts as the soil, in this case, enabling the plant to grow properly and have sufficient support.
On top of it, it ensures the same level of support as soil without having any soil-bourne diseases. So, the hydroponic growing media intakes the nutrient solution water absorbs it and therefore leads the nutrients directly to the plant roots.
Finally, the growing media helps maintain a perfect balance of nutrient-rich water and oxygen in hydroponic systems. While there are systems like Deep Water Culture that don’t require any growing media, it’s an essential component of any other system.
Crucial Factors To Consider With Growing Media
Just like with organic compost for soil-based planting, growing media for hydroponics also fulfills several purposes. That’s why you can choose the best hydroponic media for your system based on several crucial factors.
These are the main characteristics of the specific growing medium:
- Water Holding Capacity
- Air Filled Porosity
- Cation Exchange Capacity
These are the traits in which various growing mediums differentiate from one another. You’ll also be choosing the best hydroponic medium based on these properties and their impact on your system, so let’s take a closer look.
Relevance of Water Holding Capacity In Growing Mediums
In essence, the water holding capacity of a growing medium signifies the amount of nutrient solution it can absorb. Different hydroponic systems need a different level of WHC for proper plant growth.
It’s also based on the nutrient solution supply of your system. For instance, the nutrient film technique system benefits from lower WHC since the water is directly in contact with the plant roots. So, the relevance of having a growing medium, in this case, is more related to support purposes, rather than to absorbing the nutrients in the medium itself.
However, with systems like wick systems, you’ll need a higher WHC medium. In this system, small thin channels are used to spray the roots with the nutrient solution. Still, it’s not that precise so having a high-WHC growing medium can help absorb all the nutrients and lead them to the roots.
For instance, coco coir is a great option for a high-WHC growing medium. It helps contain nutrient solution water that’s eight times its weight, so you can use it for systems like wick hydroponics.
On the other hand, one example of a low-WHC hydroponic medium is hydroton. It’s in fact made of clay balls that are great for the stability of the plant and supportive for the roots but doesn’t absorb much water.
There are some options like grow stones that reach the golden middle of WHC.
Air Filled Porosity Trait
Hydroponic growing media with small particles are perfect for holding moisture and allowing easier oxygenation. That’s why the air-filled porosity should always be a focal point when choosing the best medium for your system.
Most hydroponic systems need high air-filled porosity that allows air to flow through to prevent any chance of rotting. Again, coconut coir makes a great option for this purpose, as it’s consisted of tiny particles that allow high moisturizing and easy airflow.
Perlite is also a great choice for this purpose as it eliminates the drainage possibility.
Why Is Cation Exchange Capacity Important For Growing Media?
Cation exchange capacity is essentially a trait of the growing medium to capture cations like Manganese, Copper, Zinc, Magnesium, Calcium, and Potassium. This helps with the control of nutrient intake.
Low cation exchange capacity reflects the nutrient absorbing capacity in a way that the medium can’t hold nutrients easily. However, this doesn’t have to be a bad thing, if you are growing plants that don’t need many cations as nutrients to grow steadily.
So, with a growing medium like rock wool, you can control the nutrients that reach the roots of your plants. On the other hand, using a high cation exchange capacity medium like coco coir might need an adjusted nutrient solution to maintain the balance.
The Best Growing Mediums For Hydroponic Systems
Now that you know some of the main factors to consider when choosing your hydroponic growing medium, let’s discuss some of the best options. Hydroponic growers have different preferences in choosing the best media, and it also depends greatly on the type of system you are using.
Still, these are the most frequently used medium in creating a perfect growing environment for your plants:
- Coco coir
- Expanded clay pellets
- Perlite
- Gravel
- Rockwool cubes
- Parboiled rice hulls
- Oasis cubes
It’s always best to use organic materials for growing medium, and we’ll lead you through all the mentioned media.
Coconut Coir And Fiber
The coconut industry often disregards coco coir, so you are doing both yourself and the environment a favor by using this organic medium. It’s best used in hydroponics as a growing medium that has a high WHC and a sort of balanced CEC and AFP.
That’s why it’s perhaps among the top 3 most popular media for hydroponics and it works well in all sorts of systems.
It’s extremely lightweight, yet it absorbs up to 8 times its weight in nutrient water solution. It retains water for systems that rely on the hydroponic growing media to keep the water in between irrigation cycles.
Coco coir or coconut fiber naturally reflects any potential bad fungus from forming in your system. It can also be used for entire growing cycles without being replaced, and the only thing that you might want to pay attention to is the type of nutrient mix used with it.
Since coconut coir isn’t among the solutions with the lowest CEC, you might need to find a balanced nutrient solution. Because of this, you might want to boost nutrients like Magnesium, Calcium, and Iron to reach the balance.
Expanded Clay Pebbles
Clay pellets are another great and frequently used option in hydroponics. They come in a wide range of sizes that you can opt-in for, and are pH neutral which is a great starting point for adjusting the pH of your nutrient solution. It’s a lightweight expanded clay aggregate with small holes for oxygen intake.
You can use them for several growing cycles until they start to deteriorate, so that also makes them convenient. One thing that you’ll have to be especially careful about is the WHC of this growing medium.
Expanded clay pellets don’t absorb water so well, so you can only use them for systems where it’s not crucial to have a medium with high absorbance. Hydroponics like Ebb and Flow systems can benefit from expanded clay pellets as a growing medium.
These systems rely on the direct nutrient water supply to the roots with the flood channels and the clay pellets make a perfect stable option for plants to grow in.
Perlite As Growing Medium
Perlite is a lightweight growing media that allows high oxygenation for the plant roots. It consists of small particles and allows better airflow. However, it can easily be washed away in Ebb and Flow systems, as well as other systems where the flood cycle brings water in contact with growing media.
So, you might want to use it in a mix with other media like coconut coir. It’s made of volcanic glass and provides proper stability for your hydroponic plants to thrive. Still, it’s not the best option WHC-wise, since it quickly drains and requires frequent irrigation cycles.
Using Gravel As Growing Media
Gravel is yet another frequent choice for hydroponic farmers to use as growing media. It’s extremely cheap and you can even use aquarium gravel for hydroponics. It requires washing before it can be used as growing media.
It’s best used for hydroponic systems where the growing media is not in direct contact with plant roots. Gravel dries quickly, so it’s not the best option for Drip systems or other hydroponics where you rely on media absorbency to bring the nutrients to the plant roots.
Rockwool Cubes
Using Rockwool as media for hydroponic growing is also one of the frequently used options. It’s a great growing media in terms of water retention, so you can use it for systems with not-so-frequent irrigation cycles.
It enriches the plant roots with nutrients absorbed, but it might require some pH adjustment as it usually has high pH. You should also be careful as a grower since Rockwool might cause skin irritation, so it’s sometimes better to use coco coir.
Rice Hulls
Parboiled rice hulls make another solid hydroponic growing media for hydroponic growers. They absorb nutrient water and allow for fewer irrigation cycles, and it doesn’t hurt to add as much of this medium as you want into your system.
It won’t affect the balance and it even makes a more sustainable solution than coconut fiber. They also have high air porosity, which is perfect for systems that demand high root oxygenation.
Using Oasis Cubes As a Hydroponic Growing Media
Oasis cubes make a perfect substitution for Rockwool as they are made of floral foam that’s not as hazardous for hydroponic growers as Rockwool. It’s also quite affordable as a growing medium and can be easily found.
Also, it makes an environment that doesn’t allow any bacteria from forming and comes with a pH level that’s much like the natural growing soil pH. All you need for the seeds to germinate in oasis cubes is a sunlight spot and nutrients.
Final Thoughts
Choosing a growing medium for hydroponics doesn’t have to be as hard as you think it may be. You need to consider whether you want an organic material or something that includes some synthetic compounds like floral foam.
Also, it’s crucial to also think about airflow, cation exchange, and the absorbing capacity of the medium. With this guide, you should be able to choose the best option based on these factors and the hydroponic system of your choice.
Frequently Asked Questions (FAQ):
What growing medium is the best for hydroponics?
It all depends on the WHC, air porosity, and cation exchange when choosing the best hydroponic medium for your system. Some of the most popular options are certainly Rockwool, clay pebbles, and coco fiber as these are traditionally used in many hydroponic setups.
Do I need growing media for hydroponics?
Some hydroponic systems like DWC don’t use any growing media and rely on deeply submerged plant roots in a nutrient solution for proper growth. However, other systems need a growing medium to add stability for roots to spread like Ebb and Flow systems, as well as some systems like Wick and Drip systems that need the medium to absorb the nutrients.
Which growing media can be used for the most different hydroponic setups?
You can mostly use clay pebbles and coco coir for various hydroponic systems. These are the most frequent media along with Rockwool which is sometimes replaced with floral foam.
Can air be a growing medium in hydroponics?
Some hydroponic systems like aquaponics rely on plant roots being free in the air for oxygenation and occasional sprays of nutrient water for moisture.