Category Archives: grow medium

Pros and Cons of using Rockwool

Rockwool one of the popular growing mediums used in hydroponics systems. What are the pros and cons of using Rockwool as a growing medium? For a long time, Rockwool has been a favorite growing medium among many hydroponics gardeners. However, there are some concerns about this growing medium. Here are pros and cons of using Rockwool in hydroponic systems.

Pros of Rockwool 

High water and oxygen retention capacity 

The structure of the Rockwool allows it to absorb and hold sufficient amount of water and air. This reduces the constant need to pump water to the system. Also, Rockwool provides the root system with the much-needed oxygen.

Available in various shapes and sizes 

Regardless of the type of your hydroponic system, you can find Rockwool that meet your needs. Rockwool is available from small cubes to huge slabs. Moreover, Rockwool is locally available and can be found in most hydroponic stores.


This growing medium is made from rocks subjected to very high temperatures. In this case, Rockwool is durable and will not break down or fall apart. Therefore, Rockwool can be used in hydroponic systems for many years.

Easy to inoculate with beneficial microbes

Just like other growing mediums, it is easy to inoculate Rockwool with beneficial microbes. However, you may need to apply the microbes more frequently. These microbes are vital for the healthy growth of your hydroponic plants.

Easy to monitor 

You can use water content meter to monitor the nutrients, temperature, etc. This will assist you in providing optimum conditions for your plants.

Cons of Rockwool 

Non- Biodegradable 

Rockwool is designed in such as way that it cannot break down quickly. Therefore, discarded Rockwool can sit in the landfill indefinitely. In this case, it is advisable to avoid buying new Rockwool each growing season.

Have no natural occurring nutrients 

Other growing mediums such as coco coir contain naturally occurring nutrients such as potassium and other minerals. However, you have to supply all nutrients when using Rockwool. This makes you plants to rely on hydroponic nutrients at all stages of growth.

Pose health hazards 

Just like asbestos, Rockwool is made from rocks and minerals that have been proven to be hazardous. In this case, it is advisable to wear a mask when handling this growing medium. Although it is not harmful as asbestos, it is still a threat to your health. Moreover, Rockwool can cause irritation to the skin and may cause serious long-term effects.

pH fluctuations 

Rockwool has a naturally high pH which can slow down the growth of your plants. The pH of Rockwool is prone to fluctuations. This requires constant monitoring of the pH level of your system, which can be time-consuming.

Requires pre-treatment 

Unlike other growing mediums, the growers have an obligation to treat Rockwool before using them in hydroponics. Rockwool is soaked in pH treated water for the whole day before transferring plants to it. Although this is not a major concern for many people, others may feel inconvenienced when using Rockwool.


Rockwool is a growing medium that has gained popularity in hydroponic systems. However, there are pros and cons of using Rockwool.