This guide, we will give you the most popular types of hydroponic growing media. Every hydroponic gardener has their own preferences, so we will give you the advantages and disadvantages of each medium so you can choose the one that works right for your situation.
Coco Peat / Coco Coir
Coco peat 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 of Coconut Coir
Usually organic
Sustainable
Compactable (buy compressed, expand at home…saves money on shipping)
Downsides of Coconut Coir
Holds a lot of water and may drown plants
Clay Pebbles or Clay Balls
What Are Expanded Clay Pellets?
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 of Expanded Clay Pellets
Reusable
pH Neutral
Do not compact
Downside of Expanded Clay Pellets
Heavy
Drain and dry very fast, roots may dry out
Strip mined (environmental concerns)
Oasis Cubes
What Are Oasis Cubes?
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.
Benefits of Oasis Cubes
Inexpensive
No presoaking
Downsides of Oasis Cubes
Not sustainable
Not organic
Useful for germination only, not as a full growing medium
Perlite
What is Perlite?
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 of Perlite
Lightweight
High oxygen retention level
Downsides of Perlite
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!
Starter Plugs
What Are Starter Plugs?
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.
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 of Starter Plugs
Compact
Great for starting seeds
Relatively sustainable
Downsides of Starter Plugs
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.
Rockwool
What is Rockwool?
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 of Rockwool
Great water retention
Easy to dispose of
Downsides
The Danger of Rockwool
Gravel
What is Gravel?
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 of Gravel
Very inexpensive
Easy to clean
Drains well
Downsides of Gravel
Heavy
Plant roots may dry out
Not suitable for certain hydroponic systems
Gravel 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.