Hydroponic growing is a method of cultivating cannabis in a water and nutrient solution. There are different variations on this method, with or without the help of a growing medium. By definition, however, the plants are grown without soil.

Efficiently used by the Aztecs, this method dates back to 382 B.C., where plants were fed through a nutrient solution and not a growing medium. As soil is its own ecosystem with ever-changing bacteria, nutrient quantities, and pH, it’s less reliable and stable. When dealing with just water, these variables are more easily controlled. With proper growing techniques, this process can lead to higher quality bud and better yields.

Although this method involves the predominant use of water, the roots still need something to grab onto. You can’t just drop a seed into a nutrient-filled pot of water and expect it to grow. This is what we’ll be covering in this article; identifying the different growing mediums as well as their advantages and disadvantages.

Hydroponic growing medium

HYDROPONIC GROWING MEDIUMS

As you probably already know, hydro substrates do not contain nutrients. The grower is responsible for feeding the plant through a nutrient solution in the water. The roots are in constant contact with water; the growing media is nothing but a substrate for the plant to develop a root system. This gives the plant structure and keeps the roots away from light, making them believe they’re underground. It provides great oxygenation for the root system, leading to robust health and more efficient nutrient uptake.

This method has its advantages and disadvantages, obviously. With hydro plantations, growers need to be more attentive to their plants. Although plants mature quicker, nutrient deficiencies and other problems also develop faster. However, with a big enough investment, growers can set up an automated system. This will require no more than a few weekly minutes to maintain. This is complicated to setup, but has its perks. With enough understanding, hydro plants won’t catch soil-borne diseases and are less likely to develop pest-related issues.

Mediums like perlite, gravel, sand, and volcanic rock have been widely popular in hydroponic grow rooms. But with the increasing popularity of the method, new substrates have appeared on the market. Mediums like clay pebbles, rockwool, perlite, coco coir, and mapito are now being used and experimented with. Below, we’ll approach these substrates in greater detail.

CLAY PEBBLES

This is arguably the most popular growing medium in hydroponic operations nowadays. You’ve probably seen them in vases with plants and flowers of all shapes and sizes. These small, brown spheres provide excellent oxygenation for the roots. This way, they tend to grow amazingly if proper irrigation is provided. The roots aren’t placed under any stress and grow easily, making nutrient absorption extremely efficient. Don’t buy the cheapest ones. Make sure you find some that are already washed and have been adjusted for pH. This way, you won’t have to worry about these steps later, which is a very tedious process.

clay pebbles hydroponic

ROCKWOOL

An excellent insulating material and very popular in hydro plantations too, rockwool is an awesome medium for your cannabis to grow in. It has great oxygenation as well as water retention properties. Although, it takes experience and time to get everything up and running. Before placing your germinated seed, the pH of the slab must be around 5.5. To do this, immerse the rockwool in a nutrient solution with a pH of around 4.5 and an EC (Electric Conductivity)/ nutritional value of 0.5-0.6. This process should take around 24 hours. If the pH is not at the desired value by then, immersing the slabs again will be necessary. This should be done for a few more hours, checking regularly until the pH is stabilised.

Rockwool hydro plantation

COCO COIR

Popular amongst Asian grow operations, coco coir results from natural waste of coconut plantations. It’s made from the outer shell of the coconut. It’s renewable, holds moisture better than soil, and absorbs water very efficiently. It even contains naturally present nutrients, a neutral pH value, and is usable for up to 5 years. It’s an excellent option for indoor plantations as it does not develop fungi, even though it retains water for a long time.

Coco Coir hydroponics

PERLITE

This is a mineral that, when heated to a certain temperature, expands to several times its size. Perlite is relatively inexpensive and easy to use, therefore it’s a popular option as a growing medium. It has excellent aeration and retention properties. It is also a very popular medium to be mixed with soil in a soil-based plantation. Although in this case, for hydro grow rooms, it works perfectly on its own. It should be noted that perlite is non-renewable, although it is reusable. This is important for environmental concerns, yet its long life cycle can help cancel out the non-renewable factor. It is a medium that will not degrade or decompose, remaining usable for years. It has a neutral pH, which will take on the acidity or alkalinity of a desired nutrient solution. On top of that, it can be washed and dried, returning itself to the neutral pH value of 7.0.

perlite hydroponics

MAPITO

Popular amongst Dutch growers, mapito is a mixture of rockwool and coco coir. Another medium with great oxygenation and moisture retention. This medium should be treated before placing the seed in a similar way to the rockwool method mentioned above. The substrate should be placed in a bucket of water with an EC level as low as 0.3-0.4. This medium comes in flake form, which brings several advantages. Contrary to the rockwool and coco coir bricks, mapito allows the grower to move the plants. It becomes easy to pick up the flower from the vase to check the root system or move into a larger pot.

Due to its flakiness, this medium provides even better oxygenation than the original substrate bricks it’s composed of. For the same reason, it also retains and absorbs water more efficiently. But the fact that it's looser also means that you can’t press it too hard when getting it into your net pot. This may cause stress on the roots with the added difficulty of trying to pierce through the material.

mapito hydroponics

WHICH IS THE BEST OPTION FOR YOU?

There is no perfect option out there. Growing cannabis is not an exact science. It all depends on a series of factors that growers will have to assess for themselves. We hope this article served as a beneficial introductory guide to the different mediums out there. Now, you can now make an informed decision for your grow operation. Making mistakes is part of being a grower. This is how you learn. With experience, you’ll find the best medium for your plants and for your routine. Certain ones will require more work with better yields, while others will require little to no attention, but won’t give you the best buds. We just hope we helped you take your first step in starting a hydro grow.

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