Types of Stonewool Blocks

Posted on April 27, 2020 by Red Rock Block

Stonewool at RedRock Block: Offering Endless Solutions to Commercial Hydroponic Needs

Stonewool is a versatile material that has uses across many spectrums from the construction industries to the many types of horticulture industries. This cheap, lightweight, highly absorbent, and extremely efficient material is excellent for soilless grow media applications on any scale of production. This material is known for its ability to distribute water and plant nutrients in a uniform  manner that makes it more ideal than soil media applications.

What is Stonewool? 

Stonewool is a lightweight material that is made from the spinning of molten basalt rock. This spun fiber is spun into fine fibers that can be shaped and formed into a variety of shapes and sizes.

Stonewool can also be formed into a range of cubes, slabs, and granular products. This material is made from natural rock and is considered as an all natural material. This material is widely used as a media in commercial horticulture for the production of a wide range of crops from strawberries, tomatoes, melons, peppers, herbs, cut flowers, and more!

Stonewool wasn’t always used in the horticulture industry, but rather it was solely used as an insulating material in the construction industry.

It’s All In the Moisture Gradient!

One of the most important factors of stonewool is the ability of the material to drain freely after irrigation and contains a relatively balanced ratio of nutrients, air, and fibers.

The ratio differs based on the brand and products, but the products are balanced and consistent. Typically the material will contain roughly 80 percent nutrient solution, 15 percent air space, and 5 percent stonewool fibers.

One of the other important characteristics of stonewool is the ability of the material to also extract water for growth with low moisture tensions in the media. This means that the plants are able to easily extract water with ease when the material is saturated and when the slabs have dried down (up to 70-80 percent dried)- in other media this would lead to plant stress and wilting.  There are countless other benefits of stonewool that make this material one of a kind and ideal for all hydroponic systems. Reference the

Want to find out more? Check out RF Agriculture’s article on Soilless VS Traditional Media to see the comparison between the two. 

RedRock Block Product Line

Depending on the setup of the hydroponic operation and the types of crops grown, the operation will need to select stonewool blocks that are best suited for the job. RF Agriculture provides a wide range of stonewool products that can be used for any crop and stage of growth in a growing season. From cubes, blocks, slabs, and covers, RedRock Block is ready to provide only the best of stonewool products for the industry’s leading large-scale producers and growers.

Stonewool Plugs and Small Cubes

Even though stonewool cubes are small, they hold a tremendous amount of water, which provides an excellent buffer in between cycles in a hydroponic system or in the case of a system shut-off.

Cubes on average will hold roughly 18 percent of oxygen between the stonewool fibers which provide excellent oxygen to the roots. This also reduces the chances of over-watering significantly. Cubes are typically used as a media to germinate seeds and propagate cuttings. The 1.5:” cubes are typically used for starting seeds or starting cuttings, while the larger cubes are used as a media for compact crops on a smaller scale. 

Seeds that are germinating are delicate and require a balance of water and air. Too much water and seeds will rot, not enough and the seeds will wilt and die off. Stonewool has the ability to create a homeostasis of moisture content for the seedlings allowing them to germinate without water stress of either too much or too little. Cubes can also be easily transplanted into larger slabs and blocks later in the growth cycle reducing transplant stress and stunted growth that is usually associated with transplanting to larger containers. Larger cubes and slabs either have the precut squares for cubes or can be customized to spacing and cube size for larger transplants.

Stonewool Blocks


The stonewool grow blocks have the same properties and benefits as the grow cubes, but on a larger scale.

Blocks give the plant more room to grow with ample root zone space and more support.

The ease of transferring from cubes to blocks is very high as the cubes can be placed in hole precut or custom cut by the grower.

The materials are the same and as the root systems grow, the roots will grow into the additional material with ease. Temporary pinning may be required to ensure stability until roots are able to grow into the new material.

Stonewool Slabs

Stonewool slabs and stonewool flowering slabs also have the same properties as the cubes and grow blocks, however, slabs offer the grower versatility in spacing and the ability to customize a grow block through cutting slabs down.

Slabs can give more root zone space and can have cubes transplanted into cut holes that are spaced specifically to plant needs.


RedRock Block currently offers two different types of stonewool grow slabs-

  • RedRock Grow Slab – 99x15x7.5cm – 36-Inch x 6-Inch x 3-Inch (12/Cs) (16 Cs/Plt)
  • New Stonewool Flowering Slabs – RedRock SOLO Flowering Slab – 30 cm x 20 cm x 10 cm – Hole Size 10 cm x 10 cm (Case of 18) (32 Cs/Plt)

Grow Block Covers

For added protection and support of plants, blocks and slabs can be covered with plastic covers. These provide extra protection from the elements such as excess light, pests, disease, and algae growth while still providing nutrients and oxygen flow to the plants. These plastic grow block covers also extend the life of the stonewool cubes, blocks, and slabs. 

Brand Product
DripCap Plastic Block Cover (Standard)
Floraflex Flora Cap (Various Sizes)     4”,  6”,  8”Floraflex Light Sheild- 6”Single Use Flora Cap
Grower’s Edge Growers Edge Block Covers
HydroFarm Hydro Farm Block Grow Block Covers

The use of stonewool in the commercial hydroponics operation has many benefits such as increased water conservation, better plant growing conditions, less stress to the plants, higher yields, and increased performance of space.

Additionally, stonewool products are very versatile and can be customized specifically to the crop and needs of the operation. A greenhouse operator needs to refer to their budgets and overall goals for the selection of the stonewool products to be used, as well as the specific needs of the crop. RedRock Block has experts that have decades of combined experience in the field to assist in making recommendations and product selections to meet the needs of the operation.

Find out more information about RedRock Block commercial-grade stonewool grow blocks and slabs today! Call- 1-310-967-2025

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