Stone wool is an excellent way to grow large crops with a small amount of space and growing medium.
In this article, we break down rockwool as a growing media. How can it hold moisture and air? We also cover the differences between organic soil and rockwool, checking pH levels, times to water plants grown in rockwool cubes, and which Atami nutrients are best to use.

Small stone wool cubes are great for germinating seeds.
Small stone wool cubes are great for germinating seeds.

What is the growing media stone wool, also known as rockwool, made from?

Stone wool as the name suggests, is a wool material made from rock. The way the stone wool is produced is via heat treatment until the rock becomes a molten state. From this point, slabs can be woven together and then cut down, depending on the final size of the cubes. If you visit your local grow shop, you will notice that the cubes are available in small, jiffy-sized cubes, designed for germinating seedlings or rooting clones.


The sizes will range from germination-sized, 4-inch, 6-inch slabs, which are typically around 1 meter in length and created to sit in trays. One of the main reasons why stone wool is the preferred method of growing medium in the vegetable and fruit markets is that the substrate contains absolutely no nutrients, allowing the grower to administer the feed and EC at will.

Stone wool germinating trays are easy to use and give remarkable results.
Stone wool germinating trays are easy to use and give remarkable results.

The benefits of growing plants using rockwool cubes

● Stone wool can hold a large volume of water and nutrient solution.
● Plants grown in rock wool with hydroponic nutrients will produce large crops.
● Perfect for growing in small spaces and in a greenhouse environment.
● Ideal and easy to set up with top-drip irrigation systems on a large scale.
● Plant roots will grow very well inside rock wool due to the air pockets inside.
● Stone wool contains no nutrients, so you are in full control of E.C levels.
● Seeds and clones planted in rock wool can easily be transplanted to bigger cubes.
● Stone wool slabs and drip lines can be used to make large-scale farming simple.


The differences between hydroponic rockwool and organic soil

If you have been thinking about making the switch from organic methods to using stone wool with hydroponics, then the main differences really are the fact that nutrients are provided via nutrient solution. Unlike soil, which takes 72 hours for organic material to break down and buffer, using rockwool with hydroponic nutrients is far more complex and requires checking pH and EC levels.


Growing fruits and vegetables in soil is highly forgiving and is the perfect entry level for an enthusiastic grower. Stone wool is far more challenging as far as what can go wrong. But once dialed in, working with stone wool over soil will pay off when it comes to the final size and weight of your harvested crops.


How does stone wool hold moisture and air for a plant’s roots?

Thanks to the way stone wool is woven together, air pockets are trapped inside. This makes stone wool a growing medium with excellent water retention, wicking ability, and air exchange between waterings. In fact, when it comes to which growing medium holds the most water for the longest periods of time, rock wool will always be superior to coco and soil. A plant’s roots can easily penetrate the rock wool fiber while accessing a consistent film of nutrient solution.


Which plants are well suited for stone wool?

If you are a green-thumbed enthusiast who loves to grow your own produce at home but is not quite happy with the overall yields each season, then why not try using rock wool? Tomatoes, strawberries, and herbs. Melons, cucumbers, peppers, and chilies will thrive in stone wool medium, and the yield potential is endless!


Soaking rockwool, checking pH and the best time to water.

Stone wool when in a dry state, will have a high pH level close to 8 on the scale. This means that you will need to soak the rock wool cubes or slabs before planting them. You will want to lower the pH to an optimum range of between 5.5 and 6.5. To do this, immerse the cubes slowly to expel all the air. Let them soak for 2-3 minutes in pH-adjusted water.


Once you have found the sweet spot and the optimal pH range, you can now soak the cubes in a mild nutrient solution to give seedlings or clones a head start. When your plants have reached a generous size and have become fruit bearing, you may find feeding more than once per day is possible with rock wool.


Setting up a drip irrigation line connected to a water pump and reservoir will be the best way for you to maintain pH, E.C and water temperature. Using a 15-minute segment timer allows the plants to be systematically fed the same volume of nutrient solution at the exact time every day, resulting in a far more consistent crop.

Large vegetable producers use this method, ensuring consistent results.
Stone wool germinating trays are easy to use and give remarkable results.

Will I need new rock wool cubes after each harvest is complete?

Unlike soil or coco, which can be reused after harvesting, used rock wool will need to be thrown out. Stone wool can only really be used once; however, it is not an expensive material to buy and is extremely easy to source.


Which Atami nutrients product can be used for rockwool and hydroponic systems?

If you are ready to grow the biggest, brightest and best-yielding tomatoes, strawberries, melons, peppers, chilies and herbs, then we recommend using B’cuzz Hydro A+B combined with B’Cuzz Root Stimulator and B’Cuzz Booster Uni. Our grow guide charts are easy to follow and will provide the best results.



Stone wool has become a popular growing media for commercial-scale farming thanks to its ability to hold great amounts of water and air. Fruits and vegetables grown in rock wool cubes with a top drip irrigation stake can produce enormous harvests compared to organic methods, making this growing medium highly efficient and easy to replicate on a large scale.


It is important to fully understand how pH levels can affect nutrient uptake when growing plants in a hydroponic system using rock wool. We recommend following our nutrient guide feeding chart to ensure you will grow the best possible crop. Good luck!

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