Aquaponics Grow Media
How to find the Best Grow Media for your Aquaponics System
As we have discussed in other pages, aquaponics combines aquaculture (raising aquatic animals such as fish, snails, crayfish, and prawns) and hydroponics (growing plants without soil) into one integrated system. Ammonia in fish waste is broken down by bacteria and converted into nitrites – and then nitrates – to be used as fertilizer for the plants. It is clear that the main components of a recirculating aquaponics system are the fish tank, fish, grow beds, plants, and pump. But did you realize that the aquaponics grow media you choose is also an important consideration? Since not all hydroponics grow media is suited for aquaponics, it’s important to choose a media that will work well in your aquaponics system. With that said, let’s review some key things you should consider before selecting the best aquaponics grow media for your system. After that, we will list the top 5 mediums for aquaponics.
Why do we need grow media in Aquaponics?
Grow media serves as a support structure for the plants in an aquaponics system. Not only does the media keep plants in a stationary and upright position, but it also provides as a surface area for bacteria to thrive inside your grow beds, and a acts as a mechanical trap for the solid waste as it is expelled out of the fish tank and into the grow beds. Furthermore, aquaponics grow media serves as an exchange for oxygen and moisture, and gives worms a comfortable habitat to live in.
Some Key Consideration When Choosing Aquaponics Grow Media
Inert – Aquaponics grow media should be pH-neutral.
Size – If the media is too small, its bound to cause compaction and clogging. Large grow media is apt to cause air gaps, which can adversely affect the growth of the plants. Use an aquaponics grow medium that is roughly ½” to ¾” in size and has a good surface area for colonizing bacteria.
Weight – Aquaponics grow media shouldn’t be so heavy that becomes unmanageable, yet too light that it floats around and clogs up your system. Light to medium-weight media is ideal.
Depth – Allow for roughly 12” of grow media in your aquaponics grow bed.
Easy on the Hands – Sharp grow media can not only damage plant roots, but it can also cut your hands as you tend to your grow beds. Choose an aquaponics grow medium which is relatively smooth yet still highly porous.
No Decomposition – Aquaponics systems do not react well when grow media breaks down. Avoid grow mediums that will introduce anything harmful to the system.
Avoid Limestone – Limestone-based gravel will wreak havoc on your system’s pH-level. If you are unsure whether limestone is present, place your gravel in a cup of clear vinegar. If it starts to fizzle, chances are high that the gravel contains some problematic limestone. Another good test involves placing the rock in a cup of distilled water and letting it sit. After a few days of sitting, test the pH. If your gravel passes both of these tests, then its probably ok to use in your aquaponics grow beds..
Rinse before Using – Be sure to thoroughly rinse any dust and debris from your aquaponics grow media before using it in your system.
pH Management – Just because your aquaponics grow media is pH-neutral doesn’t mean your system won’t become too alkaline or acidic. The optimal range for most aquaponic systems is a pH of 6.5-7.0. Monitor your pH closely and adjust accordingly.
Coco Coir – As is the case with most organic grow media, coco coir tends to break down in aquaponics systems. It also holds too much moisture, discolors the water, and may even cause your pH to go out of whack. Coco may work just fine as a top layer, but we don’t recommend filling your entire grow bed with this media.
#1 – Clay Pebbles (LECA)
Lightweight Expanded Clay Aggregate (LECA) are balls of clay which have been processed at a super-high temperature to form a highly effective grow medium. It is one of the most popular media used in both hydroponics and aquaponics – and for good reason.
Clay pebbles are lightweight yet heavy enough to provide good support to a plant. They are also pH-neutral, non-degradable, and release almost no additional nutrients into the water. Their highly-porous composition and spherical shape help to maintain a beneficial oxygen to water balance while also providing gardeners a smooth surface to work with (ie, they won’t cut your hands!).
A possible downside is the initial expense of purchasing bags of LECA. However, since this grow media is totally reusable, in the long run, clay pebbles are an investment that will serve you over the course of many grows and many years. Because clay pebbles have very few drawbacks and fit every criterion for a great aquaponics grow media, they are our top pick.
Recommended Products
| Clay Pebbles (L.E.C.A.) | Important Features | size/weight | ||
|---|---|---|---|---|
| Hydro Crunch Expanded Clay Growing Media |
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• Excellent water-storage properties • No added fibers or solvents • Coarse, aerated and porous expanded clay • Works well with all hydroponic systems |
• 38 lbs. • 33" x 18" x 10" |
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| GROW!T Clay Pebbles |
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• 100% natural, pre-washed clay • Pebbles have a strong structure • Freely draining, does not retain excess water, and provides beneficial oxygen levels • Suitable for drip-feed, multi-pot and flood-and-drain systems |
• 11.3 lbs. • 19" x 3" x 19" |
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| Leca Clay Hydroponic Grow Media |
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• Made of 100% natural clay. • Pebbles are of uniform, round, inert, and 100% natural clay • pH neutral • Good for hydroponics, ensuring adequate root aeration • 1 bag will fill two 5” pots, eight 3” pots, or twenty-four 2” pots |
• 1.9 lbs. • 9" x 7" x 2" |
#2 – Expanded Shale
Like LECA, expanded shale is another great aquaponics grow medium. The silicon-based shale is mined, crushed, and then kiln-fired at high temperatures. The result is a porous, pH-neutral, and clean aggregate that is ready to use in an aquaponics system.
Although slightly heavier than LECA, expanded shale has a lightweight profile which works well in aquaponics grow beds. Each stone possesses a large surface area for producing the bacteria necessary to convert ammonia into nitrates. Expanded shale has a slightly polished surface area, so – like clay pebbles – it’s easy on the hands and will not harm the root system of your plants. Additionally, shale is reusable and typically manufactured in the USA. For all of the positive characteristics of expanded shale, we rate it as #2 on our list of best aquaponics grow media.
Recommended Products
| Expanded Shale | Important Features | size/weight | ||
|---|---|---|---|---|
| Expanded Shale 40 lbs. Soil Mender |
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• Porous •Silicon-based • pH-neutral • Great aeration and hydration properties |
• 40 lbs. |
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| ViaStone Expanded Shale Viagrow |
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• pH-neutral and porous • Lightweight and reusable • Provides high oxygen levels • Stones measure 8 and 16 mm in size |
• 50 Liters • 24" x 8" x 20" |
#3 – Growstones
Growstones are a kiln-fired aggregate made from mixing recycled glass with calcium carbonate. They possess many of the same positive characteristics of LECA and Expanded Shale – lightweight, porous, smooth surface, and pH-balanced. Growstones provide beneficial moisture and aeration to the root zone and their large surface creates an ideal area for beneficial bacteria to colonize.
That said, growstones do have a few drawbacks. For one, plant matter is more apt to collect inside the pores of growstones than other media. So while they are reusable, they should be thoroughly cleaned between grows to remove any plant debris. Additionally, there is some debate over whether growstones alter pH in an aquaponics system and whether they can break down over time. We would advise you to soak your growstones for a few days before using them and test the pH until it consistently reads neutral. And if you are concerned that growstones may break down over time, just opt for LECA or expanded shale. For the aquaponics gardeners, growstones provide a problem-free aquaponics grow medium.