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A Comparison of Coco Coir vs. Rockwool

Growing Medium's Compared

No matter what growing method that you choose, one of the biggest concerns is the growing medium that you select. Two of the most popular selections are Coco Coir and Rockwool. In this article, we’re going to take a closer look at these two growing medium options in order to give you a better idea of their pros and cons. Then, you’ll have a basis for making your own decision as which one to use.

Using Coco Coir as Your Medium

Coco Coir is derived from the ground up and the frayed husks of coconuts. It’s an inert medium with a pH that is close to being neutral. It also has the property of being able to retain water while it also will allow for sufficient oxygen to reach the roots of the plants that it is supporting. The primary use of this material is in hydroponic systems and various forms of container gardening.

You can obtain Coco Coir as small and large cubes as well as loose material for potting. The smaller disks are good for cutting and seed starter disks, while the bigger cubes for plant transference to containers/hydroponic systems. This material is valued for not only being efficient but also for being renewable. The main drawback, however, is that it can clog up drippers and pumps and facilitate the buildup of sludge in the reservoir.


Some Coco Coir Features:

  • It’s an excellent choice for tropical plants. This medium is very easy to work with and users will like the way that it can increase their yield if they haven’t used it before. 
  • Since the source of this material is something that is generally tossed in the garbage, the cost is very reasonable.
  •  It can release nutrients efficiently because of its 5.9 to 6.4 relatively neutral pH. Having nutrients released readily to plant roots will help your plants grow quickly.
  •  It’s basically easier to hydrate than peat moss and will also last longer in soil. 
  •  It requires little prep work and it’s perfectly suited for plants that are designed for tropically warm and wet climates. 

Using Rockwool as Your Medium

Rockwool (also known as stonewool) is also an extremely popular growing medium. It’s created from silica-based rock that is heated and spun until the material resembles cotton candy. Its primary advantage is its ability to have an excellent ratio of oxygen to water when supplying nutrients to a plant’s roots. Like Coco Coir, it also has a relatively neutral pH. It will also discourage root-infesting insects from propagating in your plants.


When using Rockwool, you will most likely encounter it in the form of cubes. Since you’ll find it being sold in this form, you’ll commonly use the smaller (one inch) cubes for root cutting and seed starting. Afterwards, you can then use those starter cubes for transplanting into bigger cubes. You can actually purchase the smaller and larger cubes so that they will fit perfectly with one another – the larger cubes will have a 1-inch hole that conforms to the 1-inch starter cube. This makes using Rockwool cubes a very simple process.

Growers like to use Rockwool cubes in systems such as hydroponic flood and drain setups. Using Rockwool cubes is also compatible when it comes to transplanting your cubes into other growing mediums that include; nutrient film systems, deep water culture and expanded clay (for drip). In addition, besides growing hydroponically, Rockwool can be used for starting clones that are then planted into indoor containers and even outdoor gardens.

The Pros of Using Rockwool:

  • Until the material begins to dry out, it excels at holding water. This makes it simple to work with.
  • This material is very consistent and doesn’t require having to adapt to different situations for each new batch of plants. 
  • Producing Rockwood is a highly efficient process that can produce 37 cu. ft. of material from only 1 cu. ft. of rock. In addition, the fire that is used to create the product will biologically and chemically render the final project inert. This provides a perfect medium for growing in hydroponic systems.

The Cons of Using Rock Wool:

  • Unfortunately, Rockwool is not overly friendly to the environment. Since it’s made of basalt and chalk, it won’t ever break down into simpler components. Not only that, but mining for the rock to create this material is harmful to the environment. Additionally, the manufacturing plants that make Rockwood give off air pollution composed of hazardous organic and metallic materials. So, if you’re environmentally conscious, you may prefer to use coco coir.
  • It’s more expensive than Coco Coir. All-in-all, coco coir costs about half of what Rockwool sells for.
  • If Rockwool is in a newly spun state, using it to grow can offer a distinct challenge. That’s because its pH will be higher and that can lead to plant nutrient deficiencies, which slows growth rates and will make flowering more difficult.
  • Since it needs a significant amount of buffering before being used to plant in, prepping the material can be a challenge. 
  • Rockwool can present a rather steep learning curve. This is the result of the material being completely inert. So, when you’re using Rockwool, your nutrient schedule requires pinpoint accuracy. You can have a situation in which each one of your plants needing different nutrient levels are various different times. So, a grower will need to be able to make a commitment when it comes to monitoring the growing process.
  • Finally, Rockwool will tend to dry out quickly, which will harm the plant’s root structure. Therefore, you’ll need a watering timer or prepare to be extremely careful in your observations.

Are you looking to buy Coco Or Rockwool

At The Hippie House we stock a large range of hydroponic and horticultural equipment including a great range of growing mediums. We stock Grodan rockwool cubes, slabs and granulate as well as a range of high quality coco coir and coco mixed blocks. 


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