Hydroponic Growing Media

Ed Wike
Written by
Last update:

Coco Peat / Coco Coir

Coco coir is produced by the extraction of fibers from the husks of coconuts.

The fibers are put through a separation process and the resultant product is called coco fiber or peat. This is boiled and treated with chemicals to create a material that has similar growing characteristics to Sphagnum Peat Moss.

The main difference between coco fiber and sphagnum peat moss is the source of the material and the cost.

Sphagnum Peat Moss is a natural material that is harvested from swamps in Canada and parts of Europe. Because of it’s natural source, it has a high carbon footprint, requiring many chemicals, heavy machinery, and large amounts of fossil fuel to produce.

Coco fiber is a cheaper material that is made from the fibers of coconuts. Trees rarely need to be harvested and planted to produce the coco fibers. The carbon footprint is less in this industry, but the cost of production is higher.

So, which material is the best one for you?

We recommend sphagnum peat moss for new gardeners who are learning to garden.

The material will easily pack down and hold the shape you give it. It's also does a pretty decent job at holding on to nutrients without becoming too compact.

Expanded Clay Pellets

Expanded Clay Pellets are made from clay minerals that undergo a physical expansion process.

This process produces a porous, lightweight, self-weighting and non-compacting material that is unique. It is water-resistant (except when wet) and will not shift around in the medium.

Expanded Clay Pellets are used in containers indoors or outdoors.

Nowadays Expanded Clay Pellets are widely used in potted plants and garden decoration, as organic growing medium for hydroponic systems, in municipal wastewater treatments, as fillers in sound-absorption material, as a reinforcing material in flexible-medium concrete, as filler in gunpowder, and as a filler in rubber and plastic.

Manufacturing process is environmentally friendly.

Sure To Grow

There are a few gardeners who have shifted to using hydroponic growing media (often called hydro) and discovered that it offers some great advantages over container gardening. First, understanding how the media works makes hydroponic plant growing easy to get into.

In a nutshell, the growing medium is a combination of 2 components: polymer crystals and bio-char. Being composed of both of these components turns this material into a “gooey” substance that water and fertilizer is absorbed into (think Jell-o). So they’re quite easy to plant in.

The polymer crystals are hydrophilic, so they absorb water. But because they are porous, the water exits into the growing medium. Gases and nutrients also exit the media, and carbon dioxide is released, allowing the plants to breathe.

The bio-char ingredient is a rusty colored material, made from charred hardwood and/or nutshells. It’s a porous substance that retains nutrients and helps water retain its nutrients, even when the plants are transpiring water during the day.

It’s used as the support media for the plants. The polymer crystals are added to it, and then it’s evenly mixed with water until it’s the consistency of your perfect Jell-o.

Oasis Cubes

Oasis Cubes are one of the most helpful tools for indoor gardeners and hydroponic growers. These little cubes are a transplant tool, not a growing medium, but the results are outstanding.

When growing in soil, gardeners need to give seedlings a lot of care and tender love and attention to get them through transplanting. These little cubes make the process a lot easier.

To transplant seedlings using Oasis Cubes, you just fill one with water and allow it to absorb the water. When the cube gets warm to the touch, it will be ready to be placed directly onto the soil near the seedling to be transplanted.

As you can see, the watering process is simplified. Your hand or a watering can are no longer necessary to water your plants, they can water themselves. For anyone who does not like to get their hands or a watering can dirty, Oasis Cubes provide the perfect solution.

—————————————————————————-

Perlite

Two of the most common mediums for hydroponic growing are perlite and vermiculite. Both are mined products and come in similar packaging.

Vermiculite is expanded at temperatures for about 3.6 million years. The substance originates as mica, which is made of shiny silicate sheets. When it is heated at temperatures of 1,400 degrees and higher, it expands a hundred times, and the sheets separate. The end result is a sparkling, lightweight mineral in irregular chunks.

Farmers and gardeners have favored perlite for a long time. The substance benefits growers due to its larger pore size and excellent drainage characteristics.

Vermiculite is a heat expanded magnesium silicate. Once mined, it is water soaked at high temperatures and pressures. This causes the chunks to expand to about forty times their original size. This expansion also creates a fluffier final product.

So what are the differences in the final products?

Vermiculite is ideal for starting seedlings since the larger particles allow for optimum air infiltration, while retaining moisture. Once the seedlings are transplanted, it can be used as a mulch and a top dressing.

Vermiculite is hard to decompose and it does not break down easily while in the ground. The large size of the chunks may also allow for excessive surface runoff.

Starter Plugs

If you are a beginner you will need to decide on what growing media to use in your hydroponic system. You have a couple of options.

One choice is to use starter plugs. These are like little plug plants. There are usually 16-18 per tray. There are three sizes of starter plugs available. The most popular size is 12-14gram weights. The smaller ones are 6-8gram weights. Within the starter plug category are 3 main types, square plugs, round plugs, and super round plugs. The reason I mention the shape of the plugs is that this is where your decision making should start. Are you going to build your own hydroponic system? Are you going to buy a premade system? What kind of system are you going to build or buy?

You can build a system for both square and round plugs, but not for super round plugs. You will need to make sure that your growing media support brackets are capable of supporting super round plugs.

Rockwool

In order to grow plants hydroponically, you need to provide them with a substitute soil.

One of the most popular options is rockwool. Many people use it, and it does have some great features. But it's not your only option. There are a couple of other things you may want to consider.

Rockwool, which is also a common choice for container gardening and indoor plants, is a manufactured fiber made from molten basalt. Because it comes from the ground, it has many of the same qualities as soil.

In this way, it is a helpful alternative for organic gardeners.

However, it does have some drawbacks. For one thing, it is porous.

That means that it absorbs incoming moisture and holds onto traces of fertilizer and solution. This is fine when you are using soluble formulas, but if you use one with micronutrients, you could have a problem.

Because the minerals are held in the crystalline structure, they won't be available to your plants. Some experts recommend soaking the rockwool completely, and letting it sit for an hour before using so that the minerals can leach out.

Growstones

The reason there is not much online about Growstones is that the company is just getting started. Growstones are a new type of growing medium, made from a special form of lava rock. The shape of the Growstone follows the natural contours of the lava stone. The unique shape of the Growstone makes for a great growing medium for hydroponically grown plants.

The Growstone media is fully porous and made from a renewable resource … volcanic rock. This volcanic rock is heated and altered to create a new stone, which is then crushed to the shape of the traditional Hydrogarden grow stones.

The major advantage of Growstones is they are fully porous. Water and nutrients are readily available to the root system, which allows for quick growth. The porous nature of the Growstones also provide a CO2 scrubber for the roots. The Growstone media also has an optimal pH level of 7.

The result is a healthy environment for the roots.

Growstones are a natural, organic soil replacement that is fully biodegradable and made from a renewable resource.

Growstones fit perfectly in your existing HydroFarm system.

But you can also use them in NFT, drip, Ebb and Flow or Wick systems.

The Drawbacks of using Growstones are basically their production time and their cost.

Rice Hulls

Rice hulls are exoskeleton of rice plants that are removed during processing. They contain no food value, so rice hulls are available for free or very cheap at rice mills and is a preferred growing medium for Hydroponic growing. Rice hulls are a strong ingredient that are very effective, absorbent, remain loose, and allow the capillary action the plants need to absorb water and nutrients.

Rice hulls are easy to use because there are no salts or synthetics to add to them. Rice hulls need to be rinsed to remove dust and dirt and drain well. They must be stored in a cool dry area to keep them from molding, and need to be aerated to prevent this from occurring.

The main drawback of using rice hulls is they are hard to aerate. Plus the hulls break down quickly and can clog the system. All products need to be pure and not used even once before they are planted. They should be stored in an area free of sun that is dry. These are the main things to take into consideration when dealing with rice hulls.

Pumice

Pumice is fast becoming the growing media of choice in hydroponics, aquaculture and soil-less gardening. This lightweight volcanic sediment is non-toxic, pH neutral, sterile and highly absorbent. Because it is porous, pumice releases oxygen to the root zone and creates a favorable habitat for beneficial microbes.

Pumice holds 8 times its weight in water and is also used to brew beer and make bread. It is soft enough for use on tender cuttings but firm enough to support the plant as it grows. This airy, light rock is also mined to produce an abrasion resistant lining in high-impact athletic shoes. Ideal to support growth in the early growth stages, pumice stone is becoming a standard for root zone media in hydroponic farming.

Sand

Sand can be used for growing hydroponically. It is easy to find and may be free.

However, be aware that river sand when used for growing plants can leach minerals. That is why it is recommended to only use cultivations grade sand.Cultivations grade sand is washed and sieved to achieve the right size.

Sand can be used for greenhouses or terrace gardens as they absorb extra water. Because of this they are used in desert areas to catch extra water and have a slow release.

Sand is easy to clean. At the end of the season one sweep with the rake is all that is required.

Sand is nice as it has little debris so it can be placed in a terrace garden without worrying about small branches or other debris.

Sand loses the most moisture of any growing media so you will need to water more than you would with other growing media.

Sand is not a good idea for weed control as its rough surface causes the roots to tear easily.

Gravel

Gravel is one of the most popular growing media for hydroponic gardening. It’s very accessible and inexpensive, and for this reason it’s often promoted as a starter growing medium for micro-gardeners.

However, it has its limitations. Gravel is heavy, which makes it costly to ship. Plus, it’s very hard to clean, so the risk of introducing pathogens to your system is high. On the other hand, it retains water very well. This makes gravel perfect for containers that have a drain hole, and it’s very versatile when it comes to nutrients, as it can accommodate both liquid and solid types.

The disadvantage of gravel is that it’s an inert growing media. This means that it doesn’t hold on to nutrients very well. Also, it slowly releases nutrients that your plants will take up. However, this can be used to your advantage, as it allows you to add extra nutrients to the water, to achieve specific nutrient targets.

Wood Fiber

In the hydroponics, the role of the growing medium is to provide a support system for the roots and provide resources to the plants.

Generally, the growing mediums come in two types; geolite and soil.

The soil option uses natural additives such as compost, peat moss, or bark, to add nutrients and moisture.

But the downside is that it is heavy, hard to handle, and has a larger absorption rate, which means you would need to keep a close eye on the pH balance or the plants may get too much or too little.

As for the geolite, it is best in hydroponics due to its excellent water holding capacity, low weight, and unlimited life span. But you still need to add your own nutrients.

The use of wood fiber especially pine or redwood, eliminates the need for excessive supplements, such as nutrients and soil supplements due to the natural properties of the fiber.

The wood fiber provides the medium with the right amount of nutrients, moisture, and light for optimal growth.

As a result, you can cultivate a variety of plant species.

To get the best performance, the wood fiber should be replaced every six months, otherwise you need to add more nutrients to the medium.

Brick Shards

Depending on which type of grow system you decide to create, choosing the appropriate growing media is imperative. For a hydroponic system, the main choice typically come down to one of two things, ceramics and rock wool. While rock wool is typically chosen for hydroponic systems, it does have its downside.

One of the biggest issues with rock wool is that it is like liners for your drain pipes and your kitchen sinks. They are all very efficient at their job, which is why they are ideal in a number of situations outside the grow room. Unfortunately, this efficiency includes absorbing almost all of the water sent to them. They can also take a very long time to re-absorb water if they have absorbed a lot.

Given the state of most grow systems, this takes a lot of the control unwillingly out of a grower’s hands … at a very inopportune time. Instead, using a system like brick shards can not only help tremendously with odor control, it also has the benefit of encouraging water evaporation at a much higher rate.

Polystyrene Packing Peanuts

The Flaw

What do you think of when you think of a packing peanut? Probably something like the air filled polystyrene spheres used by Amazon and other large online retailers to prevent damage to fragile product during shipping.

But besides manufacturing packing peanuts, there are a couple of companies that have done some pretty amazing things with this product. As a result, these empty air spheres are finding their way into all sorts of products from disposable cups to buildings.

While polystyrene packing peanuts may seem like the ideal product for a hydroponic grower looking for an inexpensive growing media, there is also a downside to using them.

Using packing peanuts as a growing media for hydroponics is a disappointing experience. Because these Styrofoam polystyrene coverings are used to protect delicate items, they have to be free of any contaminants.

Specifically, they are manufactured to be free of any chemical compounds that could cause personal injury or cause damage to the fragile items they are shipping. These same chemicals will find their way into your hydroponic growing system, and eventually into your living plants.

Polystyrene packing peanuts have been banned by most states. The plastic compound that makes them so light and airy causes them to dangerously break down and release toxic chemicals into the ground. That means that most of these air filled polystyrene spheres are not recyclable.

Vermiculite

Vs. Rockwool for Growing Media

Rockwool and vermiculite are two names used to describe like growing mediums. Both are expansions of mined minerals that are used in agriculture. Where they differ is in their particle size and ability to hold water. Rockwool can hold more water than vermiculite.

Rockwool comes from a huge material created in an environmentally friendly process that begins by mining magnesium-rich and calcium-rich rocks of a certain hardness in locations in the US and UK. The rock is crushed and mixed with alkaline water in which it steams and expands to many times its original size. Excess water is drained from the mounds allowing further expansion into a loose fibrous material.

Vermiculite mines a mineral bed between granite and basalt rock heated by magma. Steam from the heated minerals combines with rainwater and creates a highly absorbent expandable mineral.

In hydroponic systems, rockwool and vermiculite are used to retain water, supply nutrients to plants, and provide support. The growth medium also protects plants from the environment.

Which is better for your application?

Rockwool:

The better expansion rate allows for faster plant growth.

Ability to plant into rockwool gives the grower better control over nutrient levels.

Due to its higher porosity it is able to hold more nutrients.