It’s Time For You to Make a CRUCIAL Choice: Coco Coir or Rockwool?


It’s Time For You to Make a CRUCIAL Choice: Coco Coir or Rockwool?

There are many choices professional cannabis cultivators must make. Selecting the best substrate for your needs is just one of them. 

Most professional growers examine substrate characteristics to find the best choice for their needs. In this post, we’ll take a look at two substrates-coco coir and Rockwool–and weigh the pros and cons of each so that you, the grower, can make an informed decision before investing your time and money. 

Coco coir and Rockwool are the substrates cultivators use most often in hydroponic growing systems. And for a good reason. Both have qualities hydroponic growers need: good aeration to the root zone and easy nutrient and pH management. 

But no two substrates or growing situations are quite the same. So let’s have a closer look.

What are you looking for?

You must understand what to look for in a substrate to make an adequate comparison. Here are some factors you should consider when choosing the suitable substrate for you:

  • Aeration and drainage
  • nutrients
  • ability to retain water and nutrients
  • ease of use
  • cost
  • availability and environmental impact

Coco Coir

Growers are increasingly choosing coco coir as their preferred substrate. Besides hydroponics, you can use coco coir in virtually any growing situation, including potted plant production, in the field, and your home garden.  

Manufacturers like us process coco coir from coconut husks that would otherwise go to waste. We soak the husks for months in salt or freshwater (Riococo prefers freshwater), and once harvested, process everything into compressed bales for shipment. Most of the coco coir people use for horticulture comes from Sri Lanka and India (Riococo coco coir hails from Sri Lanka). 

Coco coir enthusiasts love the substrate for many reasons. It’s inert when processed correctly, so it’s relatively easy to establish and maintain a fertilization program. It’s also an accessible medium for the beginner cannabis grower. If you find problems in a crop, making corrections is relatively straightforward because, unlike peat-based growing mediums, the media is nutrient-free. The pH of coco coir varies between 4.8 and 6.8, so, like any growing media, you must closely monitor and make adjustments accordingly. 

Coco coir is a sustainable product, which is another factor that appeals to growers (and the consumer). Coco coir easily breaks down in the environment like any organic matter (leaves, grass, etc.). And in some situations, you can reuse or compost coco coir. 

Here’s a central selling point: coco coir costs less than Rockwool. 

There are very few downsides to cultivating cannabis in coco coir. Some folks think coco has a high salt content because of its saltwater processing, but we process husks in freshwater to avoid contamination during cultivation. 

Some of the minerals, most notably calcium and magnesium, won’t be available to the plant due to coco fiber’s cation exchange capacity (CEC). This may require a supplemental feeding of calcium and magnesium or CalMag in the cannabis vernacular.


Rockwool was developed in Denmark in the 1970s and today is practically synonymous with hydroponics. It’s manufactured from volcanic material called basalt rock. Manufacturers heat the material into molten lava and spin it into fibers. The final result is an inorganic substrate that doesn’t break down in the environment like plant-based substrates. 

Some growers appreciate Rockwool’s ease of use and consistency. And as we’ve already mentioned, Rockwool is a durable substrate that won’t break down during the crop cycle. You can use it in NFT hydroponic systems to grow most vegetables, herbs, and flowers. 

Like coco coir, Rockwool is an inert substrate devoid of nutrients. As such, you can easily manage the environment around the plant’s root system. Should you encounter problems during the crop cycle, like an increase (or decrease) in pH, or a nutrient deficiency, you can make changes with relative ease. 

Unlike coco coir, Rockwool isn’t sustainably harvested, nor does it break down in the environment. There are also concerns about product safety if you’re exposed to Rockwool for lengthy periods, although the current data is inconclusive. Still, it’s best to err on the side of caution – you don’t want to harm yourself, your employees, or worse, the end cannabis consumer.

A tale of two substrates. 

Coco Coir and Rockwool are the two mediums that hydroponic cannabis growers rely on the most. Coco Coir is more versatile because you can also use it in non-hydroponic growing situations, including home gardens. Both mediums are readily available and provide good aeration to the root zone of plants. Manufacturers mine Rockwool from non-renewable sources, while Coco Coir is a sustainable product harvested from coconut waste material.  

Ultimately, it’s you, the grower, who must choose the suitable substrate for your growing situation. Whichever substrate you choose, be sure to choose a reputable company that will provide a consistent product from bale to bale or slab to slab.