Guide to hydroponic growing media

Added on 14 October 2021

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In a hydroponic farm, plants grow in water rather than soil. But without the traditional soil as a growing medium, hydroponic growers have a tough question to answer: which growing media is best for my hydroponic farm? The most common media options are coconut coir, rockwool, peat moss, and perlite. We'll discuss these and others below.

Coco Coir

Coconut coir, or coco coir, is a byproduct of the coconut harvesting industry made from the rough, brown, fibrous husks of coconuts. You may also see it called coco peat, coco-tek, or ultrapeat. It's an entirely organic material that is highly inert and holds water exceptionally well. It's an environmentally friendly product, completely renewable, and can be composted when no longer needed. Many growers use it in a 50/50 ratio with other media like clay pellets or perlite because it may hold too much water if used alone.

Pros

Organic
Eco-friendly and sustainable
Excellent water-to-air ratio

Cons

Doesn't drain well, should be mixed with other media
Must be replaced after a few uses

Rockwool

While rockwool might sound like a very stiff and scratchy sweater material, it's actually a fascinating material for hydroponic growing. The material is created by melting rock down and then spinning it into fibers, similar to fiberglass. These rockwool fibers are then pressed into cubes of different sizes, often used for sprouting hydroponic crops.

Unfortunately, the medium has some pretty serious drawbacks, even though plants seem to love it. It doesn't ever break down, so it's almost impossible to dispose of. It's also not very environmentally friendly medium to produce. Rockwool cubes often have a very high pH and must be soaked before they're used. And the dust of the fibers can be an irritant to your eyes and respiratory system.

Pros

Retains water well
Good aeration

Cons

Dust is an irritant and possibly carcinogenic
Cannot be disposed of
Not environmentally friendly
High pH, must be soaked before use

Peat Moss

Peat moss has been in use in farming for centuries, primarily for packing plants and for compost. It is a dead fibrous material found in peat bogs, which are typically cool, wet environments. Today, many hydroponic growers use this naturally occurring material as a growing medium.

Peat moss, sometimes sold as Jiffy Plugs or Grow-Plugs, retains water and plant nutrients well. It commonly offers several years of use from a single plug, so you won't have to replace it as often as some options. And unlike organic compost, you won't have to worry about it hiding any weeds or microorganisms. Unfortunately, peat moss is not a renewable resource, taking thousands of years to form, so it's not the most environmentally responsible option available.

Pros

Good water retention
Holds up for years
No concern over weeds or microorganisms

Cons

Not renewable
Acidic
Can be expensive

Perlite

Among the most common growing media available, perlite is already familiar to many soil-based farmers and gardeners, who have been using it for years as an aerator for soil mixes. This medium is made from a form of volcanic glass, which occurs naturally and has excellent oxygen retention. It looks like rough white gravel. Perlite is an excellent choice for long-term crops, but be careful. Because it is so light, it can easily be washed away in certain types of hydroponic systems.