Types of Hydroponic Growing Media

Author: Kevin Espiritu, Epic Gardening

Although growing hydroponically is soil-free, this doesn’t mean that there is nothing to support our plants.

In most hydroponic systems, growers use different types of hydroponic media to help support their roots and maintain a good water/oxygen ratio.

In this guide, I’ll give you a breakdown of the most popular types of hydroponic growing media. Every hydroponic gardener has their own preferences, so I’ll give you the advantages and disadvantages of each medium so you can choose the one that works right for your situation.

Coco Peat / Coco Coir

Ground Coconut Husks / Coco Coir

What is Coco Coir?

Coco coir is quickly becoming a favorite among hydroponic gardeners. It’s made from ground up coconut husks and represents a giant leap in hydroponic growing media.

To understand why ground coconut husks are becoming so popular, let’s take a look at what a coconut husk does for a coconut. Coconuts are grown in tropical regions, and often times they fall into the ocean when they are ripe. The husk protects the seed and flesh from sun and salt damage. Most importantly, the husk acts as a great growing medium for the coconut to germinate and create new trees.

Now apply these benefits to hydroponics. The ground up coco coir will act as a great hormone rich and fungus free medium for our plants. In the same way that it helps the coconut to germinate, it will help all of our seeds and seedlings to start strong. Coco coir has a great air to water ratio, so we don’t have to worry about drowning our roots. Best of all, it’s completely renewable. Coconut husks would generally go to waste or be composted if they weren’t used in hydroponic applications. Here, we’re taking what was once a waste product and re-purposing it to grow more plants!

Growing Tips

When coupled with fabric pots moisture problems can be avoided.

Built up salts can often be a problem, but there are many lines made particularly for coco that allow for easier flushing. Try using Canna Coco and Smart Pots.

Benefits of Coconut Coir

  • Usually organic
  • Sustainable
  • Compactable (buy compressed, expand at home…saves money on shipping)

Downsides of Coconut Coir

  • Holds a lot of water and may drown plants

Expanded Clay Pellets

Hydroton Expanded Clay Pellets

What Are Expanded Clay Pellets?

Arguably one of the most popular media to use in days past has been hydroton expanded clay pellets. As their name suggests, these are made by expanding clay to form round balls of porous material. 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.

In my experience, the only two downsides to using hydroton pellets has been their weight and their draining ability. In certain hydroponic systems, like ebb and flow, filling up an entire flood table full of hydroton is going to leave you with a very heavy system. They also drain and dry out very fast because there is much more space between each pellet than other hydroponic growing media. They can be used to great effect to line the bottom of an growing tray, when draining is an issue. Other than these two disadvantages, hydroton pellets are a great, reusable media to use!​

Benefits of Expanded Clay Pellets

  • ​Reusable
  • pH Neutral
  • Do not compact

Downside of Expanded Clay Pellets

  • Heavy
  • Drain and dry very fast, roots may dry out
  • Strip mined (environmental concerns)

Reader Experiences

Endlessly reusable, but heavy and drain poorly – can dry out roots.  ​Works great as a reusable medium and allows for easy plant and root removal. Roots sometimes get entangled in the pellets but generally they are easily cleaned.

Perlite

Perlite – Light as Air

What is Perlite?

Perlite is something that many traditional soil gardeners already recognize. It’s a soil-free growing medium that has helped to add aeration to soil mixes for years. It’s created by air-puffing volcanic glass to create an extremely light and porous material. It has one of the best oxygen retention levels of all growing media because of how porous it is.

Its weight can be a downside in certain hydroponic systems where water interacts directly with the growing media, causing it to shift around and wash away. Because of this, perlite is rarely ever used alone – typically it is mixed with coco coir, soil, or vermiculite.

Benefits of Perlite

  • Lightweight
  • High oxygen retention level

Downsides of Perlite

  • Too lightweight for certain hydroponic systems
  • Strip mined (environmental concerns)
  • Potential particle inhalation danger

Growing Tips

Straight perlite growing is one of the tried and true methods of hydroponic production. With virtually no cation exchange this media is a great option for longer term crops; especially in drain-to-waste scenarios. You have to watch out for moisture deficiencies as it holds absolutely no water!

Starter Plugs

What Are 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.

For those who are concerned about sustainability and organics, 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 downward 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.

Benefits of Starter Plugs

  • Compact
  • Great for starting seeds
  • Relatively sustainable

Downsides of Starter Plugs

  • Only suitable for starting seeds or cloning

Growing Tips

If they remain wet and fungus gnats are a problem in your area, the gnats will infect the plugs.

Growstones

What Are Growstones?

I came across growstones a while back at a hydroponic expo and fell in love. The company takes discarded glass bottles from landfills, crushes them into a powder, melts the powder, and mixes in some calcium carbonate. It bubbles and then they cool the mixture and break it up to form what looks like lava rocks.It’s extremely lightweight, sustainable, and a great medium in almost any application. The one downside I’ve run into is that you typically can’t reuse it because roots will stick to it after harvest and ruin sterility.

Benefits of Growstones

  • Lightweight
  • Great air to water ratio
  • Sustainable

Downsides of Growstones

  • Hard to clean