What is the hydroponic growing medium?
Hydroponic growing mediums are materials in which plants grow. In traditional cultivation, you mostly use soil as a growing medium. But in hydroponics, you’re not limited to just soil.
Therefore, in addition to focusing primarily on finding the best hydroponic systems, do not forget to look for suitable materials for growing plants. The growing media is an important part of Hydroponic equipment for Hydroponic Grow Systems
What makes a great hydroponic growing medium?
After excluding all objective factors, the ideal medium is the one which
- It is organically produced, biodegradable, and environmentally friendly
- Maintains an even ratio of air and water.
- It has a medium cathexis capacity to retain nutrients.
- It helps protect plants from pH changes over time.
- It is economical and easy to find
- It is light enough and easy to carry
Of course, it is difficult to meet all the required criteria, but in this post, I will give you the necessary details about the most popular growing media used in Indoor Hydroponics Systems; the Advantages and disadvantages of each material. Most importantly, I will help you decide which growing media will be best for your situation.
Perlite is a very common hydroponic growing medium that has been around for years, usually used by traditional gardeners to aerate soil mixes.
As a mined material, a form of volcanic glass, perlite is formed under intense and rapid heat. Then countless tiny bubbles pop up like popcorn. So as you can guess it is very light and porous.
Perlite is a good choice for a wick-type hydroponic system because it has excellent standing suction. But due to its porous and easy-flowing nature, I do not recommend using this medium for fast and powerful irrigation systems such as ebb and flow. It is swift and easy to wash.
Capable of holding air very well, and having a neutral pH but flowing easily, perlite is rarely used alone. People often mix it with other growing media such as vermiculite, coir, or soil – a common combination is with vermiculite in equal amounts (50-50).
One caveat when working with perlite is that because this medium contains small and porous particles, you should protect your inhalation when working with perlite. Pre-wet it and then rinse it to prevent dust from bubbling up.
- Reasonably cheap
- High air retention.
- Lightweight, not suitable for certain types of systems.
- Media dust – effects on the environment and health
- Can be used in drip systems, and aeroponic systems.
Vermiculite is a form of hydrated laminar minerals that resemble mica.
Like perlite, vermiculite is processed by subjecting the material to extreme heat and expanding it into small, clean, odorless pellets.
Vermiculite is an excellent soilless planting medium. It is non-toxic, sterile, moisture resistant, and has a near-neutral pH. What’s more, the material is very light and can retain water very well, which is quite a contrast compared to perlite. However, it does not retain aeration as well as perlite.
This Hydroponic growing medium also has a reasonably large cathexis capacity to help store nutrients for later use.
There are different types of vermiculite, so be aware and choose the right material for hydroponic purposes.
And because of its ability to hold a lot of water (about 200% to 300% of its weight), there is a risk of suffocating your plants. Hence it is usually used in combination with other media. The most well-known of these would be perlite, as the two media complement each other quite well – perlite drains so quickly while vermiculite retains moisture.
They are often combined in a 50/50 composition, which prevents the mixture from being washed away in tidal systems.
Can be used in drip systems, and aeroponic systems.
- Retention of water and nutrients
- Poor drainage capacity
- Risk of plant suffocation
Rockwool would not seem so strange For hydroponic wool growers as the material has been widely used in recent years, mostly on commercial farms. And this material turned out to be quite effective, hence its popularity.
This sterile, porous medium is primarily composed of granite and/or limestone rocks that are heated until molten and then spun into super-thin, long fibers. Then people compress these fibers into cubes, bricks of preferred sizes.
Rockwool has many advantages of an ideal growing material, such as resistance to microbes, good water, and air retention. This protects your plants from dehydration while providing a continuous amount of available oxygen to the plant roots.
However, there is one word of caution regarding the pH level when using mineral wool. The natural pH of the material is usually high, which can change the pH of the nutrient solution. Avoid this by soaking this medium in pH-balanced water before use.
Another disadvantage is that mineral wool is non-degradable and unsustainable. Unused mineral wool fibers are almost impossible to dispose of.
Dust released from the media can also cause irritation. This is not good for the lungs and eyes, so it is good to wash it in water once after use.
From what I’ve heard lately, many hydroponics enthusiasts have stopped using hydroponics mainly because of their sense of environmental care and responsibility. Many growers do not want to use products that bring pollution from their production process and cannot be disposed of, which is the case with mineral wool.
Overall, however, Rockwool is a highly effective hydroponic growing medium.
- Great capacity for water absorption and aeration
- It is not environmentally friendly
- Dust is not good for health.
- Disturb the pH of the nutrient solution.
- It can be used in drip systems, ebb and flow systems, deep water cultivation systems, and nutrient film technology systems. Almost any system except aquaponics.
Expanded Clay Pellets
Expanded clay pellets or hydroton (also referred to as LECA (Lightweight Expanded Clay Aggregate)) are small, marble-sized, round spheres. They are created by heating and expanding clays to form thousands of tiny bubble-like spheres.
Overall, this is the best & effective medium for hydroponic use.
But as a form of rock, clay pellets are lightweight due to their porous nature. And yet they are still heavy enough to give plants strong support and are quite excellent at drawing nutrients into plant roots.
The round and porous form makes clay pellets an incredibly balanced medium of water and oxygen. This neutral pH medium is reusable.
Clay pellets are not good water-retaining material because of the gaps between individual pellets. They leak and dry quickly. So make sure you water the material sufficiently.
Also, pellets are heavier and more expensive than other media.
- Reusable, sustainable.
- Effective water drainage and air retention.
- Poor ability to retain moisture
- More expensive than other growing media
- It is best for drip systems, ebb & flow systems, and aquaponic systems.
Oasis cubes are made of floral foam that is designed as a leaf mold. Each individual cell of the medium (which looks like cubes) contains the right amount of nutrients and air and water for plant growth.
Growers use oasis cubes primarily as a starting medium for seedlings or plant cuttings, not as a full growing medium for hydroponics.
The medium is pH neutral. Its cells absorb water and air quite well, which is very necessary for seeds or cuttings. What’s more, roots can easily grow and expand within the open cell structure of the medium.
- Good water and air retention
- Not organic
- It is not sustainable
- It is used for the stages of germination and seedling growth.
“Coco coir” (coconut fiber) is from the outer shell of coconuts. What has once been considered a waste product is one of the best hydroponic growing medium available. Although coir is an organic plant material, it breaks down and decomposes very slowly, so it provides no nutrients to the plants growing in it, making it ideal for hydroponics. Coir is also pH neutral, holds moisture very well, yet allows good root aeration. Coconut fiber comes in two forms, coconut coir (fiber) and coconut flakes. Both are made from coconut husks, the only difference is the particle size. The particle size of coir is about the same as potting soil, while the particle size of coconut flakes is more like small wood chips.
The larger size of the coconut flakes allows for larger air pockets between the particles, allowing for even better root aeration. Also, if you use baskets to grow plants, the chips are too big to fall through the slats in the baskets. Both fiber and chips come in compressed bricks and once soaked in water, they expand to approximately 6 times their original size. Coconut fiber tends to color the water, but this diminishes over time. And you can leach most paint by soaking it in warm/hot water a few times before use.
- Excellent water retention and aeration
- Organic material
- Environmentally friendly
- Uncompressed after several uses.
- It drains poorly, so it is often mixed with other media.
Conclusion of hydroponic growing medium
The range of hydroponic growing mediums is like a full orchestra; there are so many “tools” that it can take some time to choose the best one for your “patch”, garden, or crop… But in the end, you will have to choose what “voice” you want your garden to have…
Most hydroponic gardeners prefer a fully organic medium with a low environmental impact; this is where Coco coir and fibers are the best choices.
Others may prefer natural pebbles such as expanded clay and vermiculite or even sand. Few choose synthetic materials, not only because they are not organic, but they also have several disadvantages.
Then again, you can mix your growing media to get the best “harmony” for the plants you want to grow.
Still, whatever you choose, my final tip is to invest for the long term; A pH neutral, durable, and recyclable growing medium will save you money and a lot of work in the future.
Look at it like picking a violin; a poor quality one may be good to learn the basics, but a good one will be passed down from generation to generation and will always grace us with its beautiful tones.