Hydroponics Growing Mediums

Hydroponics eliminates the need for soil. However, growing without soil still requires a medium which supports root systems and helps to maintain a beneficial water to oxygen ratio. Thus, a hydroponics growing medium (or “grow media”) acts as the soil-substitute in hydroponic growing systems. Note that, while the nutrient solution provides the nourishment for plants grown hydroponically, the grow medium merely provides the essential support-structure. Both components are needed for successful hydroponic gardening (aeroponics being the notable exception).

With that said, which grow mediums are available to hydroponic growers? Here are the most popular choices, followed by some top-picks in each category.

Clay Pebbles (Lightweight Expanded Clay Aggregate (L.E.C.A.)

Lightweight Expanded Clay Aggregate (L.E.C.A) is one of the most popular grow mediums used in hydroponics.  These pellets are essentially balls of clay – processed at a super-high temperature – to form a highly porous and effective grow medium. They are light-weight, yet heavy enough to provide good support to a plant. LECA are pH-neutral, non-degradable, and release almost no additional nutrients into the water. Being porous and shaped spherically help to maintain a beneficial oxygen to water balance. These clay pebbles are also re-usable, which makes them an economical hydroponic grow medium for years to come. Note that LECA tends to drain and dry out quickly, and may not be the best choice when using “ebb-and-flow” systems, as this hydroponics growing medium is too heavy. However, overall, these clay pebbles make a great choice for most hydroponic growing systems. Clay Pebbles are also very popular in DIY Aquaponics Systems.

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Clay Pebbles (L.E.C.A.) Important Features size/weight

Hydro Crunch Expanded Clay Growing Media

• 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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Mother Earth Hydroton Hydroponic Grow Rocks

• Pebbles have strong structure (no crushing)

• Size of pebbles are 8-16mm

• Hydroton (trademarked brand of LECA)

• Maintains moisture and oxygen balance

• 11 lbs.

• 17" x 13" x 3"

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GROW!T Clay Pebbles

• 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

• 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"

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Coconut Fiber (“coco coir”)

Coconut fiber, or “coconut coir,” is a popular hydroponic grow media. Made from the discard outer husks of coconuts, this recycled coconut coir lays claim to the most environmentally-friendly grow medium used in hydroponics. That said, it is also one of the best. Some advantages of coconut fiber include: pH neutral, anti-fungal, retains moisture, slow to decompose, and it provides plenty of aeration for plants rooting system to remain healthy. This hydroponics growing medium is not recommended for ebb-and-flow systems due to retaining a little too much moisture. Drip and wick systems are a better fit for using coconut coir. A mix of 50% coco fiber with 50% clay rocks (or growstones) have high success rates with the drip method of hydropic growing. Overall, coco coir also mixes well with a variety of other mediums to create a solid, soil-less hydroponics growing medium, or when used on its own.

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Coconut Fiber Important Features size/weight

CocoTek Bale Coco Growing Media

General Hydroponics

• Three types of compressed coco coir

• Low in sodium

• Made from coconut pith and fibers only

• Great aeration and draining properties

• 12.9 lbs.

• 6.6" x 12.7" x 13.2"

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Compressed Coco Fiber Fertilizer

Roots Organics

• Ideal natural pH level for uptake of nutrients

• Composted and aged for 24 months

• Cleaned to remove sodium content

• High fiber content provides beneficial air to water ratio

• 9.5 lbs.

• 5.6" x 12.7" x 13.2"

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Coconut Coir Fiber

Individual Brick

• pH neutral, biodegradable, disease-resistant

• 100% organic, no odor

• Effectively retains water and stores nutrients

• Adding warm water to the brick will enable the grow medium to expand

• 8 oz.

• 4" x 2.5" x 4"

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Growstones

A mix of recycled glass and calcium carbonate comprise another popular hydroponics growing medium: Growstones. These are unevenly-shaped (yet not sharp-to-the-touch), lightweight, and porous, making them an effective hydroponic grow medium, providing beneficial moisture and aeration to the root zone. Growstones are not considered a reusable hydroponic grow medium, however. Plant matter tends to remain inside the pores of these stones, which making them unsafe to reuse in future growing endeavors. All things considered, the inherent properties of growstones make them one of the top choices as a hydroponic grow medium.

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Growstones Important Features size/weight

Growstone Hydroponic Substrate

• Balances air and water content efficiently

• Hold more water and air than Hydroton

• Suitable for most hydroponic systems

• 98% made from recycled glass bottles

• 15.6 lbs.

• 7" x 16" x 33"

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Growstone Super Soil Aerator

• Porous, helps retain water, oxygen and nutrients

• Made from 98% recycled glass bottles

• Enhances aeration and drainage when using coco coir

• 11 lbs.

• 3,5" x 32" x 15"

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Growstone Coco Mix

• Soilless mix of Coco coir and growstones

• Blend uses quality coco fiber and 100% recycled growstones

• Mix includes redwood fiber with mycorrhizae (for added nutrients)

• Great mix for use in recirculating hydroponic systems

• 26 lbs.

• 32" x 4" x 21"

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Perlite and Vermiculite

Creating a soilless mix containing perlite and/or vermiculite are a common grow medium used in hydroponics, and are often blended with coconut fiber to form a hydroponic mix. Perlite and vermiculite are very similar media: both composed of minerals, synthesized under high-heat to produce a light-weight, pH-neutral, porous, and water and oxygen-retentive hydroponics growing medium. Perlite is a more commonly used grow media in hydroponics. Vermiculite tends to hold nutrients more efficiently than does perlite, which can be an advantage or disadvantage (depending on how much nutrition and water retention your particular plant needs). Because these media tend to be light-weight, some growers have encountered issues where the pebbles become loose, float into the pumps of hydroponic systems, and cause clogging issues. Therefore, choosing larger, horticultural-grade perlite and vermiculite may prevents this problem, along with blending these media with coco coir – or another medium – to keep the perlite, or vermiculite, stationary.

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Perlite/Vermiculite Important Features size/weight

Horticultural Coarse Perlite

PVP Industries

• Great aeration and drainage

• Retains nutrients and water

• Sterile, pH neutral

• Excellent choice for hydroponics

• 20 lbs.

• 4 cu.ft.

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FOXFARM BIG & CHUNKY PERLITE

• Super aeration and drainage

• Sterile and pH neutral

• Retains water and nutrients

• Coarse and large size

• 1 L, 2L, 4L, 8L, 12L

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PLANT!T Super Coarse Perlite

• Porous, pH neutral, sterile

• Water and nutrient retentive

• Provides aeration and drainage

• 14.8 lbs.

• 6.5" x 17" x 25"

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Premium Grade Horticultural Vermiculite

Eve’s

• non-toxic, sterile

• high retention of water and nutrients

• aeration and drainage capabilities

• 11.2 oz.

• 2.1" x 7.5" x 12.4"

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Rockwool

Rockwool is a popular grow media used in hydroponics, composed of rock (granite or limestone) which is heated, melted, and spun to form long, thin fibers. On the upside, rockwool makes a great seed-starter medium, is porous, sterile, retains moisture, and generally provides similar benefits to other grow media. On the downside, rockwool is non-degradable, which means it essentially lasts forever. Additionally, rockwell has a high pH level and requires soaking before using. The dust from rockwell can be harmful to humans, so caution is advised. That said, Rockwool has a good track of being an effective grow medium for hydroponic growing.

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Rockwool Important Features size/weight

Grodan A-OK Rockwool / Stonewool Starter Cubes

• Great for starter seeds, root cuttings, clone plants

• 200 individual rockwool / stonewool grow cubes are included

• Ideal size to fit in standard growing tray

• Bulk packaging means more savings

• Planting holes pre-drilled, making for easy plant propagation

• 12 oz.

• 4" x 8.5" x 10"

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Rockwool Starter Cubes

• Effective for cuttings, cloning, and starter seeds

• Excellent size to fit in a flat growing tray

• Planting holes are pre-drilled

• Provides seedlings ideal water and oxygen retention

• 49 Cubes

• 1.5" x 10.1" x 10.2"

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Grodan Rockwool Plant Plugs

• Plant starting plugs, featuring a slit to easily insert rooted cuttings

• Works well with aeroponic EZ clone machine

• Fit into the holes of standard rockwool blocks

• Inserted into any type of growing media

• 4.8 oz.

• 50 pack

• 17.5" x 2.5" x 9.2"

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Oasis Cubes

Oasis cubes are used as a hydroponics growing medium for starting plants. In recent years, many hydroponic growers have shifted from using rockwool cubes to now using oasis cubes for this purpose, although they both work in a similar way. Oasis cubes resemble that green, foam-like material often found supporting those store-bought plants. Because of their open cell structure, Oasis cubes can absorb air and water, but are not as susceptible to become waterlogged as rockwool cubes. Another benefit of Oasis cubes over rockwool is that no pre-soaking is required. Negatives include: not organic and not environmentally-sustainable. Overall, Oasis cubes are a good choice for hydroponic propagation.

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Oasis Cubes Important Features size/weight

Oasis Horticubes

• Highly porous and pH neutral

• Excess water is drained from the base of the germinating cutting or seed

• Ideal size to fit in standard growing tray

• Provides ideal air and water balance

• 8 oz.

• 19.4" x 9.8" x 2.9"

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Oasis Rootcubes, by Hydrofarm

• For hydroponic seed germination

• Ideal balance of water and oxygen, even when oversaturated

• High draining, low density foam

• 1.08 lbs.

• 10" x 22.25" x 22.25"

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Rapid Rooter Replacement Plugs

General Hydroponics

• Fortified with micronutrients for root growth

• Plug matrix contains a great air-to-water ratio, aiding in early root growth

• Each bag has 50 Plugs for use

• 1.4 lbs..

• 3.5" x 12" x 10.5"

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Lava Rocks

Lava rocks have a long history of being used as a hydroponics growing medium. Why?  Because they provide beneficial drainage, aeration, water retention, and are pH neutral. Lava rocks are also light-weight, porous, and provide trace elements (magnesium, zinc, copper, calcium, aluminum, cadmium, manganese) to plants grown in this hydroponic grow medium. A notable disadvantage is the fact that the inherent sharp edges of lava rocks have the potential to damage the root systems of hydroponically-grown plants.  However, lava rocks have many beneficial hydroponic grow medium properties, and are worthy of consideration.

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Lava Rocks Important Features size/weight

Hawaiian Volcanic Lava Rock Cinders

• Made from Hawaiian volcanic lava rock

• Lightweight and porous cinders

• Provides great aeration, drainage and trace elements

• 12 lbs.

• cinders range from 1/4" to 5/8"

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Small Red Lava Rock

Prorganics

• pH neutral

• Superb water-retention, drainage, and aeration

• Lava provides trace elements for plant health

• 15 oz.

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