Best Grow Media for Indoor Cannabis Grow

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When you are considering starting your own grow, the proper grow media is a key piece. This is what your plant will actually be growing in. With hydroponics becoming a more popular choice of growing there is a vast variety to choose from. It can be a challenge to figure out which one will be the best for your grow.

When choosing the media, it is important to choose one that both meets the needs of the plants as well as the needs of the system in place. Water retention, aeration and pH balance are all aspects that vary depending on the medium and must be considered when making the final choice. In this article, we will discuss the attributes to some of the most common grow mediums and which systems they are ideal for.

Expanded Clay

One of the more common options is expanded clay. Also known as lightweight expanded clay aggregate (LECA), which involves heating clay in a rotary kiln. The clay is heated which expands it into thousands of little clay balls. In hydroponics it is used to improve drainage. The clay is also used to retain water and nutrients while also insulating the roots if temperatures drop too far for sustainable plant life essentially helping save and protect the plants. The design that the clay displays also increases the level of oxygen that your roots will receive which means it will increase the growth of the plants.

*  Can be mixed with soil and Peat Moss to improve the system.

Peat Moss

Another useful medium to use when growing is Peat Moss. It retains a lot of moisture which makes it ideal for the growing conditions for your plants to ensure that they always have some form of hydration. Depending on the species of peat moss they are able to hold 16-26 times as much water as their dry weight. Perfect for retaining water and nutrients and in turn helping your plants receive more oxygen. However, it does need to be replaced periodically and tends to fall apart easily.

Coco Coir

A good natural fiber to use is Coco Coir. It is obtained from the husks of coconuts. It is usually used as a substitute for peat moss. Considered the best alternative because it is available almost anywhere and it is safe for the environment. The fiber acts similar to how the moss absorbs water which makes it an ideal substitute. This is a bigger risk to use depending on the source you get it from because they can be contaminated with pathogenic fungi. If you choose to use this substance the best choice would be to have it shipped over from mexico as there coir has been known to contain a beneficial fungus that prevents any dangerous substances from growing on the fibre and also helps as a natural pesticide.

The substance is renewable and can be used in drip and flood drain systems however it is recommended to avoid it if possible as it is dirty and there is a higher chance of the pumps or drippers getting clogged. If this happens it will increase the build up of unwanted debris in the reservoir which will have a negative effect on the plants if not taken care of properly. Even though, it is a good alternative to use as it will not only work but help the plant thrive as long as it is properly cared for.


The use of gravel is simple if you choose to use it. The only real downside to gravel is that it does not retain moisture well so it is almost useless in that aspect. However, it makes a good anchor for the plants to latch on to. It is ideal for growing techniques that are already set up to keep the plants hydrated on a consistent basis. 

It also increases the quality of drainage. Nutrient solutions can contain salt which build up in soils or mixes and if not drained properly can lead to the build up reaching levels that are toxic to your plants. Rule of thumb would be about an inch of gravel at the bottom of a container just to add a solid layer for the water to pass through.

* If the water is not properly drained it can lead to the leaves and roots being burned. Wash gravel before use every time as it can contain salt and other nutrients. Reusable if washed before every use. 


It is also known as “stone wool” or “mineral wool” and is primarily used for a drip hydroponic system. It is a combination of rock and sand which is spun to create fibers that are formed into different shapes and sizes. By the end of the process it becomes a firm material that is about the ideal water to oxygen ratio for plant growth. Another useful aspect of rockwool is that it is fairly pH neutral and helps prevent insects that grow on roots. It also acts a form of insulation for the plants which helps maintain their climate.

The different sizes and shapes that rockwool comes in makes it simple for whatever you are looking to do. It is diverse enough to fit any growing need you have. It most commonly comes shaped as cubes, starter cubes being about 1 inch which can then be transferred over to a larger cube that has a 1 inch hole to place the starter cube in making the process easy and efficient. 

River Sand

One of the most efficient ways to drain would be using river sand (never beach/ocean sand as it has already been compromised by other outside nutrients and salts). It not only is highly effective when draining but also retains moisture extremely well making it an ideal media to both save and purify the water successfully. 

*It can be used on its own or mixed with soil, vermiculite etc.


This substance is an additive that will enhance an existing grow. Perlite is volcanic glass that gets mined and heated to create white rounded materials which are good for seed starting. It is not to be used on its own, only to improve the process. It allows for draining to become more effective and helps retain water and nutrients. The shape of the glass also allows for more air to get to the roots which will help create a higher yield as the plant will grow more. 

Perlite comes in 3 grades: fine, medium and coarse which helps meets the various needs of gardeners.

*Do not fill more than a third of your pot with Perlite as it will cause the pieces to float.

Fresh Water Diatomite

From the fossilized remains of diatoms (single celled aquatic algae) comes this very useful substance. It is a sedimentary deposit that is almost completely pure and consists of silica. This makes it extremely effective as a natural pesticide. The composition of the substance also allows it to be great for retaining water and nutrients while allowing for great drainage and high oxygen circulation. 

*Mix with soil