7 Best Growstones for Cannabis Growers in 2024

As an avid cannabis grower, you tend to think about more ways than one to keep your cannabis as healthy as they can be. Growing cannabis can be super convenient and easy especially if you are using indoor and hydroponic systems. But before you may be able to start growing, you may need to put quite an effort to set things up. Not only a great deal of your time and effort but a great deal of your cash as well. After you’ve chosen and picked everything you need like grow lights, hydroponic nutrients, seedlings, and plants, it’s time to create the perfect growing medium. We tell you, never settle for an inferior or mediocre growing medium. To be able to produce the highest yields of healthy cannabis, you need a medium that supports the perfect balance of air and water. The best way to do this is through Growstones. 

Best Seven Growstones for your garden


Growstone GS-1

This GS-1 is indeed a great hydroponic substrate. They are engineered and made to effectively provide a good ratio between moisture and aeration to your hydroponic system. Some other substrates may just maximize either air or moisture, but Growstones are designed to efficiently allow for both better moisture absorption and good drainage.

Growstone GS-2

The GS-2 is also known as the “Mix This!” Soil aerator and grow media. It has highly porous aggregates which act as ‘air pockets’. They can significantly enhance aeration and drainage of any sphagnum peat, coco coir or composted soil based mix. This Growstone Mix brilliantly creates the ideal environment for your plants’ root systems and leads to healthy, thriving plants.

Growstone GS-3

The GS-3 is a blended professional quality coco coir growing mix. The aeration formula is made for faster drainage. This mix was designed and created for plants that are heavy feeding. Those plants may be in re-circulating hydroponic systems or run-to-waste container gardens with a unique air-to-water ratio throughout the root zone. With a super aerated root zone, this can allow for more frequent feeding per day with no risk of root rot.

Growstone GS-4

The Growstone GS-4 Moisture Coco Mix is a blended professional quality coco coir growing mix. It promotes moisture retention formula for less watering. It comes with added Mycorrhizae specially designed for hand watering of heavy feeding plants in run-to-waste containers. This mix is recommended whenever moisture and fast drainage is required for fast growing plants.

Growstone Gnat-Nix

This Gnat-Nix will be surely great for starting seeds and protecting your plants from fungus. It is made as a fine media for top dressing to prevent insects and add aesthetics. Growstone Gnat Nix is a scientifically-proven, safe, and chemical-free fungus gnat control for your cannabis. It’s not just free of harmful pesticides and chemicals, it’s made from 100% recycled glass. Your cannabis will surely love this Gnat-Nix.

HydroFarm GrowIt Clay Growstones

The HydroFarm GrowIt Clay Growstones comes in a 10-liter bag and features thousands of small brown clay pebbles. These pebbles are already washed so there’s no need to worry about dirt and debris contaminating your soil or water. In addition to this, the growstones are extremely durable so they won’t decompose over time. This can help prevent them from accidentally blocking drainage holes. Unlike many other growstones, this option works to stabilize the soil or water’s pH. The HydroFarm GrowIt Clay Growstones are hydroponic-friendly.

Cz Garden Supply Clay Pebbles

The Cz Garden Supply Clay Pebbles come in a two-pound bag. These growstones can be used in hydroponic systems and will expand once they are wet. Because of their porous exterior, they encourage plants to grow through them. This can help provide better stability as they sprout. They’re also useful for starting seedlings. They will provide seeds with plenty of moisture and oxygen so they grow quickly. These pebbles are reusable and are pH neutral.


GrowstonesGrowstone is a readily and commercially available hydroponic growing medium entirely made of recycled glass. They look like irregularly shaped and small stones and are very lightweight and also dust-free. The recycled glass is fully broken down into small, fine, and smooth pieces so that they can be easily processed. Another thing, these Growstones are inert, so it will not supply plants with any additional minerals or elements that could possibly interfere with the nutrient solution in the system. This makes them a very suitable medium for nearly any hydroponic set-up for your cannabis. Aside from being super functional, Growstones being made from completely recycled glass, are entirely eco-friendly. What makes Growstones unique among hydroponic mediums is because of the fact that they hold almost equal amounts of water saturation and air.

What can Growstones do

Growstones have not only one but plenty of qualities that make them great for your indoor cannabis grow. They boast features that surely make them a very ideal and brilliant hydroponic medium. So what can Growstones provide:

Drainage and aeration

The porous surface of each Growstone has special characteristics that can improve not only plant growth, but also root health. Having variable and different sizes and are interconnected, also the large pores allow quick air and water exchange. These features make the oxygen dissolve quickly. These Growstones also have smaller pores develop a barrier so that the oxygen-rich water can supply the roots.  The interconnected pores can offer a large surface area that is suitable for root growth.

Avoid rotting or low-risk of rotting  

Growstones are dry, this means you can water or feed your plants with nutrients more frequently. You will be able to give them an extra boost of nutrients without running the risk of waterlogging them or causing root rot. The dryness of Growstones can also prevent fungal diseases.

Versatility, flexibility, and steerability

With Growstones, you can easily make changes and adjust the nutrient levels and ratios for your indoor cannabis. They tend to be easier to adjust since they are a lot drier than other hydroponic mediums. This feature facilitates an easy transition from vegging to flowering nutrients.

Flow or capillary action

Growstones aggregates have some serious and great ability when it comes to wicking. They can pull up moisture for up to 15 cm above its waterline. This keeps the roots evenly moist at a healthy state and means you need less water in the long run, particularly in an Ebb and Flow or Continuous Flow set-up.

Release of silica

Since Growstones are made of glass, they tend to release a small amount of silica. Also in a form that is very accessible to plants. Silica has been proven and shown to improve a plant’s resistance to rot, pests, and disease. It is also a side benefit that might help your cannabis and surely will never harm your grow.

Multiple numbers of use options

Growstones, for sure, are great and ideal as a hydroponic medium. In addition to that, they are also a great additive to your soil mix. Theses Growstones can be added to any soil to effectively provide increased aeration that will boost plant health and reduce the risk of overwatering or root rot.

Other great things about Growstones

These well-appreciated grow stones can hold three times more water and 12% more air than Hydroton. They are also fully reusable making them a sustainable and an eco-friendly growing medium. They are also lightweight and are completely free of mold spore or weed seeds.

Potential drawbacks

Despite its greatness and functionality, Growstones still have their share of drawbacks. To help you deal with these possible issues, here are a few words of caution. It is important that you not only rinse well but also very carefully. Your newly-purchased Growstones, upon purchase, come coated with a fine sheet of silica. This silica dust needs to be carefully taken and washed off. And, this should be done outdoors or in a well-ventilated space. It is also ideal that you wear a mask. The dust is not only harsh on drains but also poses danger when inhaled. Also, you may need to watch their pH levels. Be sure to check your pH frequently and make adjustments as necessary. The last reminder is that you should be sure to soak the stones for a full 24 hours before using them. No worries, Growstones come with instructions you can easily follow.

How to use Growstones

Growstones are very versatile and easy to use. They are indeed considered as an ideal substrate in growing a wide variety of plants including cannabis in hydroponic systems.

Growstones drain extremely well and are made with numerous opened pores. This characteristic can effectively increase oxygen exchange between the environment and root zone. For this reason, cannabis growing in Growstones can never be over-irrigated. Because of this, the irrigation schedule can be flexible and easy to adjust to potential limiting situations.

Fast preparation

The simplest and quickest way to prepare Growstones is to simply rinse it with water for about 5-10 minutes. This will eliminate and remove any dust accumulated during shipping. However, rinsing alone will not allow you to take advantage of the pH buffer Growstones contains. In order to activate it, a certain soaking period is required.

Soak, poke, and drain

For efficient first time use, the “Soak Poke & Drain” method is recommended. It is simple, easy and mess-free.  While the Growstones are still inside the plastic lined bag, you can open a small hole or create a tiny opening at the top of the bag.  Fit a small water hose, and carefully fill the bag with tap water. Let soak in an upright position. Ideally let soak overnight.

After, you can poke small holes at the bottom of the bag to let the water drain away.  Rinse and drain once again to eliminate and completely remove any dust remaining inside the bag.

Place the wet Growstones in your system with the reservoir filled with water only, no nutrients.


Measure the initial water pH with a calibrated pH meter and allow your recirculating system to operate for a few hours.  After this, monitor and measure the pH again of the recirculating water.

Add the nutrients.

Let your system run for a while again for about 10 – 15 minutes this time with the nutrients.  Measure the pH of the nutrient mixture or solution. If necessary, you can adjust the pH to fit between 5.5 and 6.5 range. You can then achieve a pH-stable nutrient solution, which will be easier to correct and maintain later on.

Growstone features

These Growstones have a stable pH with an electrical conductivity of 0.19mmho/cm. It has a total porosity of 78%, water holding capacity of 30% and air-filled pores of 48%. Its bulk density is 0.2 g/cm3. You may be able to purchase thee Growstones in Small, Medium, and Large sizes. The Small Growstones in 2 mm are ideal for propagation mixes. Those in 5 to 12 mm or Medium are great for aeration in the soil mix. And, last in line but definitely not the least, the Large in 12 to 25 mm are perfect for most hydroponic systems.

Frequently Ask Questions (FAQs)

What are Growstones Made From?

Growstones are crafted from recycled glass beverage containers sourced from landfills or other waste glass collection points. These glass containers are crushed and ground into a fine, flour-like powder. This powder is the primary ingredient in Growstones. A natural foaming agent is added to this powder before it’s expanded in kilns to form Growstones.

Composition and Appearance of Growstones

Growstones mainly consist of about 98% recycled glass and 1.25% calcium carbonate, a natural foaming agent. The resulting product is a rigid, highly porous foamed glass material. It is crushed into varying sizes of irregularly shaped aggregates or stones.

Capillary Water Rise in Growstones

Yes, Growstones exhibit capillary water rise (wicking capacity), allowing water to wick up to 13-15 cm above the water level. This action is influenced by the pore size within and between each aggregate, dictating the height to which water can rise in Growstones. Smaller aggregate sizes result in smaller inter-aggregate pore spaces and higher capillary rise.

Reusability of Growstones

Growstones maintain their structural integrity over time, allowing for multiple uses. Sterilization between crops is advisable, with steam sterilization being the ideal method. A cubic yard of moist GS-1 Hydro Stones can be sterilized in 35-40 minutes using steam, reaching and maintaining 200°F.

Usage of Growstones

Growstones can be used in two primary ways:

  1. As a soil enhancement for potted crops, container gardens, flowering beds, and landscapes. Mix Growstones (GS-1 Hydro Stones or GS-2 Mix This!) into your mix at a 20-30% ratio.
  2. As a standalone hydroponic growing medium.

Using Growstones in Hydroponic Systems

Certain Growstones are suitable for hydroponic systems. However, not all types are appropriate, as incorrect usage can stunt root growth or alter water quality, affecting pH levels and plant health.

Steps to Use Growstones in Hydroponic Systems

  1. Verify Growstone Suitability: Ensure the Growstones are compatible with hydroponic systems.
  2. Fill a Net Pot with Growstones: Use a net pot with small holes to hold the Growstones, allowing room for root growth.
  3. Place the Net Pot in the Hydroponic System: Optionally, add soil beneath the net pot for additional nutrient supply to the plant roots.


Looking for a great growing medium or soil aerator may be a tough task for the beginners. And if you are someone who’s still having a hard time, we tell you, give Growstones a try! They are not only functional and efficient, they are also pretty-looking for your hydroponic or indoor garden. Another great thing when using Growstones is that aside from providing them with great growth medium, you are also protecting and helping the environment at the same time. These Growstones are made of recycled materials and are therefore eco-friendly. Indoor cannabis growing and cultivation usually leaves a significant carbon footprint. That is why the discovery and use of Growstones truly helps. Incorporating a renewable, reusable growing medium like Growstones into your set-up is a great and significant step to making indoor marijuana viable and environment-friendly in the long-run.

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