Hydroponics Growing media is simply a soilless potting medium. It is generally porous so it can hold the moisture and oxygen that the root system requires to grow. So, Grow Media serves two main functions in Hydroponics:
- To supply oxygen, water, and nutrients to plant roots
- To physically support the actual plant.
An essential part of any garden!
There are many different types of growing media you can use in your hydroponic system, though there are a couple of things to watch out for.
You have to be careful about the rock or particle size. Prefer to use a medium that is between 8mm and 16mm, there are some disadvantages if you go very far out of this range. If the media is a lot smaller then there’s not a much air space between the media when it’s in your bed. If the media is a lot larger, your surface area is markedly reduced, plus planting becomes a lot harder.
Hydroponics & Aquaponics Grow Media
Most house based aquaponics systems are media primarily based and demand the use of growing media. The exception to the rule is aquaponics methods that use a raft to float the vegetation in a nutrient-filled solution. In a raft based mostly system the roots of the plants are immersed in water and no develop media is required.
So, When developing your hydroponic/aquaponics system, it is imperative that you select a medium that matches your needs, will give you the biggest yields, and will be the easiest to maintain.
There isn’t one growing medium that is better than the rest. However many growers eventually favor one type over others. There are a lot of things to consider when choosing what to use as a growing medium.
The type of system you’re growing in, and how you design and build that system is the biggest factor.
The goal is still the same. You just need the roots to be moist, not soggy and saturated. If the growing media is saturated and soggy, the roots will suffocate from lack of oxygen. That situation can easily lead to roots dying, and root rot.
Which at anytime media you choose, you should consider doing a tiny analysis on what kind of media is very best for your situation. Utilizing a trustworthy aquaponics techniques source for reference would be useful in creating this option.
|Growstone Hydroponic Substrate||Medium||Acidic||Reusable|
|Water absorbing crystals/polymers||Low||Neutral||Resuable|
|Coco Fiber & Chips||Low/Medium||Neutral||Short|
|Poly (Polyurethane) foam insulation||Low||Neutral||Short|
|Slotted Net Pot/cups||Low||-||Reusable|
List of Growing Media
There are probably hundreds of different kinds of growing medium. Anything that a plant can grow in is considered a growing medium. There are man-made as well as organic (natural) mediums. Here, we’re listing all popular grow media and information about them to give you ultimately grow media guide.
Rockwool is one of the most common growing media used in hydroponics. This medium is sterile, porous, nondegradable and composed primarily of granite and/or limestone. 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 blocks, sheets, cubes, slabs, or flocking.
Rockwool sucks up water easily so you’ll want to be careful not to let it become saturated, or it could suffocate your plants’ roots, as well as lead to stem rot and root rot.
Additionally, they usually come at a high pH. To start you should pH balance a gallon of water to 6.0. Soak the Rockwool in the water for a few hours. Then you can start seeding.
The fibers and dust created in the spinning and compressing process can be harmful to the eyes, nose, and lungs. You can prevent it 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.
The rock wool is not used in aquaponics as there is the chance of fish consuming fiberglass or causing irritation.
Can be used in: drip systems, ebb and flow systems, deep water cultures systems, nutrient-film technique systems. Essentially any system except aquaponics.
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Vermiculite is a silicate mineral that like perlite, expands when exposed to very high heat. As a growing media, vermiculite is quite similar to perlite except that it has a relatively high cation-exchange capacity, meaning it can hold nutrients for later use. Also, like the perlite, vermiculite is very light and tends to float. There are different uses and types of vermiculite, so you’ll want to be sure what you get is intended for horticulture use.
The easiest way to be sure is to get it from a nursery.
Can be used in: drip systems, aeroponic systems.
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3. Growstone Hydroponic Substrate
Growstones are made from recycled glass. They are similar to grow rocks (Hydrocorn) but are made of clay and shaped marbles. Growstones are lightweight, unevenly shaped, porous, and reusable, they provide good aeration and moisture to the root zone. They have good wicking ability and can wick water up to 4 inches above the water line. So you’ll want to make sure it has good drainage or is deep enough so it doesn’t wick water all the way to the top. Otherwise like with the growing media in any hydroponic system, if the top of the growing medium is continually wet, you may have problems with stem rot. While they are made from recycled glass, they’re not sharp and you won’t get cut from it, even if they break.
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4. Pine shavings
Pine shavings are an inexpensive hydroponic growing media as well, and a lot of commercial growers use it. Generally for large scale hydroponic drip irrigation systems. Don’t confuse pine shavings with saw dust. Saw dust will become compact and water logged easily. You’ll want to make sure your pine shavings were made from kiln dried wood, and does “NOT” contain any chemical fungicides. Kiln dried to burn off all the sap in the wood that is bad for the plants. Most pine shaving products would be kiln dried, to begin with.
Where to find?: A good source to find pine shavings are pet supply stores. It’s used for things like hamster and rabbit bedding. Just make sure to read the package to be sure it doesn’t have any chemical additives like fungicides or odor inhibitors. You should be fine if it states it’s organic. Another good cheap source for pine shavings is at feed stores, it’s also used as bedding in horse stalls and they sell it by the cubic yard. If you have a choice get the largest partial size you can. The larger the air pockets between the shavings, the better aeration to your roots.
Pine shavings are a wood product, so they absorb water easily, thus can become water logged easily. So make sure you have good drainage so the shavings don’t sit in water. If there is a possibility of it sitting in water, a layer of rocks at the bottom will aid drainage greatly.
5. Hydroton Leca Clay (Grow Rock)
Also, Known as Hydrocorn/Expanded Clay, Grow rock is a Lightweight Expanded Clay Aggregate (L.E.C.A.). As their name suggests, these are made by expanding clay to form round balls of porous material. It’s heavy enough to provide secure support for your plant’s, but still light weight.
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.
Hydrocorn grow media is reusable, it can be cleaned, sterilized, then reused again. Although on a large scale, cleaning and sterilizing large amounts of grow rocks can be quite time-consuming.
Expanded clay pellets are mild body weight, porous and pH neutral (have no pH effect on the water). Moreover, Expanded clay is extremely light, comes in handy bags, it’s easy to plant in, easy to clean and sterile. However, its downside, usually very expensive. You will need to weigh up the pros and cons yourself, if you want quick and money is not the most limiting factor, then expanded clay is the go, if you are more concerned about cost and you’re willing to spend a lot more time on constructing stronger supports and moving and cleaning your media, then go for the rock. Some people like to take the middle road, you can fill the bottom of your bed with gravel/rock then fill the top half with expanded clay, this cuts the costs significantly, also cuts the weight, and makes sure that you have a nice media for planting and harvesting in.
Can be used in: The aquaponic systems, ebb-and-flow system, and the drip system are the usually recommended methods for using these clay pebbles.
Read in Detail the Complete guide to growing using Leca Clay Grow media
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6. Oasis Cubes
Oasis Cubes are similar to Rockwool and have similar properties. But Oasis cubes are more like the rigid green or white floral foam used by forests to hold the stems in their flower displays. Oasis cubes are an open cell material which means that the cells can absorb water and air. The open cells wick moisture throughout the material, and the roots can easily grow and expand through the open cell structure. While Oasis cubes are usually used as starter cubes for hydroponically grown plants, they also have bags you can fill your growing containers with.
While Oasis cubes are similar to Rockwool, Oasis cubes don’t become waterlogged as easily as rockwool cubes. Even so don’t let it stay in constant contact with the water supply, or you’ll still have water logging issues.
7. Floral foam
Floral foam can be used as a growing medium in hydroponics as well, and is similar to the oasis cubes, though the cell size is larger in the floral foam. Depending on the type of hydroponic system you’re using, and how you designed it, you may notice a couple of problems with using floral foam. First, it can crumble easily and that can leave particles in your water. Second, you’ll want to be sure it doesn’t get water logged. Floral foam absorbs water easily, so make sure it isn’t in constant contact with the water supply.
8. Water absorbing crystals/polymers
Polymer crystals are used in many industries from baby diapers, to the sports cloth rags. They are also used in gardening where the crystals are mixed into the soil to help retain moisture in the soil. Florists use them in vases to keep flowers fresh, and the colored ones make for a nice decorated display.
The crystals expand to many times their size as they soak up water. One pound of the crystals can hold as much as 50 gallons of water. The crystals come in many sizes, everything from a powder to marble and even golf ball size. Depending on the size of the crystals they can take more than an hour or two to fully absorb. When they are full of water they look and feel like a glob of jello. Once they dry out, they can be stored and reused again over and over.
The water absorbing polymer crystals are not a common hydroponic growing media, but like everything else, it’s growing in popularity. Mostly due to their increased availability. They are quite inexpensive, and reusable. However used alone by themselves they don’t allow the roots to get much oxygen/air. Being like jello they pack together and fill the air pockets. The larger size crystals are better suited for use, as it helps retain some of the air pockets between the crystals. Also by mixing some river rock or other similar growing media with the crystals will help increase the air pockets between the crystals.
Using the polymer crystals for hydroponics allows for some of the simplest hydroponic system designs.
Even on the slimmest of budgets. Simply soaking some water absorbing crystals in nutrient solution, then setting them in a container and placing your seedling’s in it, you’ve got a hydroponically grown plant. You don’t need any pumps. Just make sure there are holes in the bottom of your container, and just place your container in nutrient solution once or twice a week to rehydrate the crystals.
9. Coco Coir, Fiber & Chips
Coco chips hydroponic growing medium”Coco coir” (Coconut fiber) is actually the outer husk of coconuts. What was once considered a waste product, is one of the best growing mediums available. Although Coco coir is an organic plant material, it breaks down and decomposes very slowly, so it won’t provide any nutrients to the plants growing in it, making it perfect for hydroponics. Coco coir is also pH neutral, holds moisture very well, yet still allows for good aeration for the roots. Coco fiber comes in two forms, coco coir (fiber), and coco chips. They’re both made of coconut husks, the only difference is the particle size. The coco fiber particle size is about the same as potting soil, while the coco chips particle size is more like small wood chips.
The larger size of the Coco chips allows for bigger air pockets between particles, thus allowing even better aeration for the roots. Also if your using baskets to grow your plants in, the chips are too big to fall through the slats in the baskets. Both the fiber and chips come in compressed bricks, and once soaked in water it expands to about 6 times the original size. Coco fiber does tend to color the water, but that diminishes over time. And you can leach out most of the color if you soak it in warm/hot water a few times before use.
In the same way that perlite and vermiculite go together, coconut fiber is used primarily in a compound with clay pellets, called grow rocks.
Can be used in: drip systems, ebb and flow systems, aquaponic systems.
Sand is actually a very common growing media used in hydroponics. It’s the main growing media used at the Epcot Center Hydroponic Greenhouse in Florida. Mainly for their large hydroponically grown plants and trees.
Sand is like rock, just smaller in size. Because the particle size is smaller than regular rock, moisture doesn’t drain out as fast. When using sand as a growing media you will want to use the largest grain size you can get. That will help increase aeration to the roots by increasing the size of the air pockets between the grains of sand.
Sand is also commonly mixed with Vermiculite, Perlite, and/or coco coir. All help retain moisture, as well as help, aerate the mix for the roots. You will also want to rinse the sand well before use to get as much of the dust particles out of it as you can. One big downside to using sand as a growing medium for hydroponics is that it is very heavy. 3-4 gallons of wet sand can weigh up to 50lbs. So you won’t want to be moving it once you get it set up. Or use it in a ratio of something like 20%-30% sand and the rest Vermiculite, Perlite, or another type of growing media to reduce weight.
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11. Poly (Polyurethane) foam insulation
Polly foam is not commonly used in hydroponics, and hydroponics stores don’t carry it. But has been used as an alternative to using Rockwool or oasis cubes as starter cubes with great results.
Where to find: Polly foam is cheap and easy to find. Any hobby store or place that sells fabrics should carry it. It’s most commonly used as furniture foam, and is also referred to as “foam batting.” Also, comes in sheets or rolls of different sizes and thickness.
Make your own: You can make your own starter cubes for about one penny each using the poly foam if you get the one or two-inch thick sheets/rolls and cut them into cubes.
12. Air or Slotted Mesh Net Pot/cups
Finally, we have air — no growing medium at all. Cups are not actually media! but to support plants. These cups can be used in aeroponics or when planting in stagnant water without any media.
In many systems, the growing medium used is filled very deeply, meaning the roots are always completely submerged; however, in some systems, it is better for the root to hang freely where it gets access to the nutrient solution. Even in such a system, some growing medium will always be needed to allow the roots to anchor to and keep the stem supported; however, only a small layer of this is needed, and the root network is primarily in only air.
I feel these are going to last for years and getting popular in hydroponics and aquaponics. Why? it just easy to use, great starter. These cups/baskets promote healthy roots with even drainage. Letting the roots grow their own way, right down through the pot, allows for bigger, healthier roots.
These baskets work with any kind of media — hydroponics or soil-based. They’re also easier to clean since water runs right through the holes.
These are made from sturdy, quality plastic, and the wide lip ensures that they will fit any 3″ system.
Can be used in: nutrient film technique systems, deep water culture systems.
What to look while buying/using
- The holes should be good sized for roots to go through, but small enough that gravel does not fall through.
- Gravel would need to be slightly larger than 1mm; anything smaller would most likely fall out).
How to use:
You can use half gravel, and top half coconut coir to plant seeds directly into grow beds.
or Fill the cups with Hydroton and hang it in a container filled with nutrient solution using packing material or raft.
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13. 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.
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 down 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.
Growing Tips: If they remain wet and fungus gnats are a problem in your area, the gnats will infect the plugs.
Best Starter Plugs to Buy
14. River Rock
A free and easily available media that you can use in your system! River rock is rounded with smooth edges from tumbling down the river. Though manufactured river rock is rounded using large mechanical tumblers, it has the same end result with smooth edges.
You can use regular rocks from your backyard in hydroponic systems. Just make sure to clean and sanitize them before using it. Spray all the dirt off of the rock using the jet spray from your hose to clean it, then soak it overnight in bleach water to sanitize it. Then just rinse and use. Though using rock as a growing media is inexpensive and easy, it will get heavy quickly, so you won’t want to move it later.
River rocks are not porous, therefore it doesn’t hold and retain moisture in the root zone of hydroponic systems. Rock is uneven so it has a lot of air pockets between the rocks so the roots can get plenty of oxygen, but water easily drains down to the bottom. Rock won’t wick up moisture either, so you will need to adjust your watering schedules so the roots don’t dry out between waterings. You can mix in some Coco chips or other growing media that hold moisture with your rock to aid it in holding onto moisture longer.
Because of the good drainage property’s of rock, it’s very good to use to aid in the drainage of other hydroponic growing media’s that might otherwise become saturated from sitting in water. A layer of rock at the bottom of the growing container will keep your growing media from sitting in water at the bottom of the container, keeping it from being saturated.
15. Rice Hulls
These are the shells that surround rice. They allow for good drainage and retain little water in general. Rice hulls are a product that would normally be thrown away, so putting them to extra use in hydroponics re-purposes something that would otherwise be thrown away.
Even though they are an organic plant material, they break down very slowly like coco coir, making them suitable as a growing medium for hydroponics. Rice hulls are referred to as either fresh, aged, composted and parboiled, or carbonized.
Fresh rice hulls are typically avoided as a hydroponic growing media because of the high probability of contaminants such as rice, fungal spores, bacteria, decaying bugs, and weed seeds. Fresh and/or composted rice hulls tend to have a high Manganese (Mn) content. But problems with Manganese toxicity can be avoided as long as the pH is above 5. Which is below the normal range for hydroponics anyway.
Parboiled rice hulls (PRH) is done by steaming and drying the rice hulls after the rice has been milled from them. This kills any spores, bacteria, and microorganisms, leaving a sterile and clean product.
Rice hulls are also often used as part of a mix of growing media such as 30%-40% rice hulls and pine bark mix. The overall pH of parboiled and composted rice hulls range from 5.7 to 6.5, which is right in the pH range for most hydroponically grown plants.
Perlite is mainly composed of minerals that are subjected to very high heat, which then expands it like popcorn. So it becomes porous, lightweight and absorbent. Perlite has a neutral pH and excellent wicking action.
It is also quite lightweight, meaning that it floats. This can be a downside in certain hydroponic systems where water interacts directly with the growing media, causing it to shift around and wash away. It is not recommended for usage in an ebb and flow system (it will wash away too easily during flooding). Because of this, perlite is rarely ever used alone – typically it is mixed with Coco coir, soil, or vermiculite.
Perlite is widely used in potting soils, and any nursery should carry bags of it. However, perlite is sometimes also used as an additive added to cement. When working with perlite be careful not to get any of the dust in your eyes. Rince it off to wash out the dust, and wet it down before working with it to keep the dust from going airborne.
You may find it for a better price with the building supply’s, and/or at places that sell concrete mixes and mixing supplies.
Can be used in: drip systems, aeroponic systems.
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17. Composted and aged Pine Bark
Pine bark is one of the first growing media’s used in hydroponics. It was generally considered a waste product but has found uses as a ground mulch, as well as substrate for hydroponically grown crops. Pine bark is considered better than other types of tree bark because it resists decomposition better, and has less organic acids that can leak into the nutrient solution than others. The bark is generally referred to as either fresh, composted, or aged.
Fresh bark uses up more nitrogen as it begins to decompose, so commercial growers generally compensate by adding extra nitrogen to the nutrient solution. During the composting process, nitrogen is added to the bark and mixing it in while breaks down. So nitrogen issues are far less of a concern with composted pine bark. Ageing is a similar process but has less nitrogen added to it, so it’s better than using fresh bark, but not as easy as the composted bark. Pine bark can be found at places that sell ground mulch, as well as ground mulch for playgrounds.
Have any question? Feel free to ask in the comments. You can share your own experiences using any grow media, that may add value to information and knowledge of others. & if you have any friends who want to know more, please share this article with them. Thanks for reading!