Choosing The Best Hydroponic Growing Medium

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Hydroponic growing medium
Author avatar By Parker Curtis
March 23, 2022
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When you think about plant growth, you most likely visualize the need for nutrient-rich soil. While this has been the tradition from the beginning of time, modern cultivation practices have led to new growth systems that don’t necessarily depend on soil. A reliable hydroponic growing medium is one of these revolutionary options.

Hydroponic systems have gained much traction among marijuana growers in recent years, and understandably so. Growing plants without soil is efficient and easy to set up. All you need is a decent nutrient solution and a reliable hydroponic growing medium. 

Join us as we share reliable strategies when choosing the best hydroponics medium.

Hydroponic method of growing cannabis
Hydroponic method of growing cannabis

Do you need a growing medium for hydroponics?

Not really—it depends on which type of hydroponics system you use. Some setups, like aero and ebb and flow, for instance, are so simple that you don’t necessarily need a growing medium. 

However, the hydroponic system has its own set of requirements for healthy growth, and you cannot ignore the power of an excellent hydroponic grow medium. Using one offers a myriad of benefits like faster growth, optimized nutrient uptake, and a well-crystallized plant.

Choosing the best hydroponic substrate is important because different growing media provide varying levels of aeration and drainage—both important for healthy plant growth. Notably, each growing media works best for different types of crops.

What makes a good hydroponic growing medium?

These are the different factors to look at when choosing the best medium for hydroponics: 

1. Air, water, and nutrient retention capacity – The best grow medium for hydroponics uses a combination of different materials and techniques to retain water, air, and nutrients

2. Right pH (the substrate should be mildly acidic) – The pH value determines the amount of nutrient solubility in the substrate. The ideal pH for most hydroponics growing media ranges from 5–6, although you can choose anything between 5.5 to 6.5.

3. Good drainage – A good hydroponics substrate has a porous structure. This promotes the right amount of air and water retention while maintaining a high level of aeration for healthy root growth. 

4. Uniform particle size – The best grow medium for hydroponics should be free from coarse materials that clog the growing system.

5. Free of pathogens and pests – The substrate material should be as clean as possible, with no contaminants like weed seeds, soil-borne diseases, or insects that could interfere with plant growth. 

Hydroponic cannabis in expanded clay
Hydroponic cannabis in expanded clay

What are the different types of hydroponic growing media?

Hydroponic growing media come in various options depending on the type of system you use. Some of these hydroponic media types come in handy for applications like seed germination and growing flowers. However, the core function is offering a good substitute for soil in hydroponics.

Here are some hydroponics medium types to choose from for your system: 

Growstones 

These are any stones that have been heated to 1550 degrees Fahrenheit. This medium holds moisture well while also draining easily. Growstones are available in different colors. 

Advantages

  • Growstones don’t need nutrients. You can put them straight into the hydroponic system without pre-soaking.
  • They’re easy to work with and reduce labor costs since they don’t require any preparation before installation. 
  • Growstones are versatile hydroponics growing media, making them suitable for different types of hydroponic systems. 

Disadvantages

  • Growstones absorb all nutrients in the solution quickly, possibly leading to nutrient deficiency for plants. 
  • Since growstones have a porous structure, they break down easily after a few months. 
Growstones
Growstones

Expanded Clay Aggregate (ECA) 

ECA is a type of hydroponics medium made from clay balls. It holds water and nutrients well, making it the perfect choice for deep water culture (DWC) systems

Advantages

  • ECA offers good support for the plant roots, which provides better aeration for faster growth. 
  • It promotes uniform root development in containers or beds.
  • ECA can be reused several times.

Disadvantages

  • ECA should be sterilized before use since it can contain white powdery substances that may interfere with plant growth. 
  • ECA needs maintenance to remove the non-hydrated clay balls. 
Expanded Clay Aggregate (ECA)
Expanded clay aggregate

Pebbles, slates, and gravels 

These hydroponic media types are perfect for all types of nutrient film technique (NFT) systems like wick, ebb and flow, and flood and drain. They work well with aeroponics and are available in different sizes, colors, and shapes. 

Advantages

  • They’re excellent for growing large plants that require many roots to hold them down. 
  • Since the material is hard, you don’t have to worry about it breaking down during the growth period.
  • Gravels are reusable, while pebbles and slates can be sterilized for reuse.
  • They’re ideal materials for hydroponics systems requiring high water retention capacity. 

Disadvantages

  • Gravels can get very hot in summer, increasing the temperature of your hydroponic system significantly. 
  • Plants grown in substrates take a long time to recover from transplanting. 
Pebbles
Pebbles

Perlite 

This hydroponics substrate is produced by heating crushed volcanic rock at high temperatures. It has excellent water holding capacity with good aeration qualities. Perlite works well in most types of hydroponics systems

Advantages

  • Perlite doesn’t retain too much water, thus preventing root rot. 
  • It provides good support to plant roots in any hydroponic system thanks to its porous structure. 
  • Unlike gravels, perlite doesn’t become hot when exposed to sunlight or in heated systems. 

Disadvantages

  • It needs to be sterilized before use since it can get contaminated easily. 
Perlite
Perlite

Rock wool, slabs, and chips 

These substrates are made up of rock fibers shaped like cubes or slabs. These non-organic hydroponic growing media are excellent for flood and drain systems, NFT setups, ebb and flow systems, or aeroponics. 

Advantages

  • Rock wool cubes are lightweight, making them easy to transport. 
  • The growing media don’t take up much space since they come in small packaging sizes. 
  • They’re easy to work with, non-toxic, and simple to clean. 

Disadvantages

  • They may cause skin irritation when touched with bare hands or during the transplanting of plants. 
  • When rock wool gets wet, it can be challenging to dry. 
Growing marijuana seedlings in rock wool with the hydroponic system
Growing marijuana seedlings in rock wool with the hydroponic system

Foam matrix

Foam Matrix comprises foam pieces that hold water and nutrients well, making it perfect for DWC systems. These include floral foam, styrofoam pieces, and open-cell flexible polyurethane foam.

Advantages

  • They’re easy to clean and sterilize for reuse. 
  • Foam Matrix can hold together many plant cuttings in small spaces until their roots develop. 
  • Provides excellent support for plant roots since they can bear heavy weights. 
  • Holds nutrients and water well, resulting in faster root development.

Disadvantages

  • Plants grow slowly due to poor aeration when compared to other hydroponic media types. 
  • Foam matrix isn’t reusable since it tends to break down over time. 
Foam matrix
Foam matrix

Sand

Sand is the most common material used as a hydroponic growing media. It’s inexpensive and works well with NFT systems. Many hydroponic beginners also prefer it for its simplicity, weed-free state, and ease of use. 

Advantages

  • It provides good support for the plant roots, which reduces the risk of a plant tipping over or uprooting during heavy downpours or strong winds. 
  • It’s readily available and doesn’t need sterilization for reuse. 
  • One of the cheapest hydroponic growing medium to use.

Disadvantages

  • Sand isn’t nutrient retentive and has a poor water retention capacity.
Sand
Sand

Coco coir

Coco coir, sometimes known as “coconut fiber,” is a by-product of the coconut industry. It’s the husk and shell of coconuts after being grated for their milk. Coco coir has a pH range between 5.5 to 7, making it ideal for most crops, from vegetables to hydroponic weed.

Advantages

  • Coco coir holds water well thanks to its high air porosity. 
  • It’s an excellent substitute for peat moss since it’s sustainable and readily available.
  • It has no odor, unlike other hydroponics medium types.

Disadvantages

  • Coco coir can be difficult to wet initially due to its high air porosity. 
Coco coir
Coco coir

Hemp fiber

Industrial hemp fiber is produced from cannabis sativa plants specifically grown for fiber content. It’s one of the most eco-friendly substrates since it contains no heavy metals or harmful chemicals. 

It can be used to develop hemp stones, ropes, and fabrics. The hemp plant grows fast and requires minimum maintenance making it ideal for sustainable agriculture practices, especially as a hydroponics substrate.

Advantages

  • It holds up well when used in floods and drains hydroponic systems such as ebb and flow. 
  • It’s reusable and doesn’t need sterilization before you use it again.
  • It’s 100% biodegradable and environmentally safe for humans, animals, and plants.

Disadvantages

  • Industrial hemp fiber isn’t readily available in many areas due to strict laws on its cultivation and usage. 
  • The fibers can irritate the skin when touched. 
Hemp fiber
Hemp fiber

Sawdust

Sawdust consists of wood particles separated from sawing, trimming, and cutting. The material gets mixed with other substances such as coco coir or peat moss to improve water retention and drainage as a hydroponic medium

Advantages

  • Sawdust is lightweight and works best for ebb and flow systems where it can be used as a wick. 
  • It doesn’t retain too much moisture, making it ideal for plants that prefer an average amount of water. 
  • Can be used to generate heat when composted.

Disadvantages

  • Sawdust has poor aeration and may not be suitable for plants that require abundant root space. 
  • It has a strong odor and can attract pest infestations such as weevils and mites.
Sawdust
Sawdust

DIY hydroponic growing medium

There are many ways to make a DIY hydroponic growing medium inexpensively at home. One of these is using reverse osmosis (RO) water, sugar, and salt in a solution mixed with peat moss for your medium of choice.

Materials needed:

  • A large bucket for mixing
  • Sugar solution: mix one cup of sugar with four cups of warm water. Bring to a boil and cool completely before using it as the growing medium ingredient.
  • Salt Solution: Mix ¼ teaspoon salt per gallon (approximately) in just enough water to dissolve all the salt, which will take about one cup
  • Peat moss or another hydroponics growing medium of your choice (rock wool, perlite/vermiculite, coco coir). Use enough to fill up the bucket at least two-thirds full.

After you have all of these materials gathered together, it’s time to mix and make your growing medium.

DIY steps: 

  •  Combine the sugar and salt solutions in a large bucket. 
  • Add enough RO water to make up one gallon total. Stir well to combine. 
  • Add peat moss or another growing medium of your choice until the mixture is two-thirds full. 
  • Mix everything together well, making sure that all the ingredients are evenly distributed.
  • Let the mixture sit for 24 hours so that the peat moss can soak up all of the liquid.
  • After 24 hours, your DIY hydroponic growing medium is ready to use. Store any extra in a sealed container in the fridge, and it will stay fresh for up to two weeks.
  • Now you’re ready to start planting and growing some amazing hydroponic plants.

The resulting growing medium is easy to wet and doesn’t easily develop fungus or bacteria. It’s perfect for seedlings and can last for months. Water retention capacity increases when RO water is mixed with salt and sugar, creating a hydroponic growing media that can hold up to 2 times its dry weight in water.

DIY hydroponic growing mediums made from household materials are also good for most hydroponic systems since they’re readily available. For example, sand is good for an ebb and flow system. 

Sugar/salt solution with peat moss is great for hydroponics flood and drain systems. Rock wool cubes are perfect for aeroponics, while foam matrix works well with DWC systems.

5 tips to monitor and maintain the hydroponic system

Monitoring and maintaining a hydroponic system help ensure proper plant growth and development to its fullest. Neglecting the hydroponic system can result in nutrient deficiencies or the build-up of harmful toxins, which will eventually kill your plants.

Here are five tips to monitor and maintain the hydroponic system:

Ensuring water quality

The quality of water used in a hydroponics system directly affects the plant’s growth. Ensure the H2O you use is clean, fresh, and free of harmful substances.

Water should be free of chlorine or chlorination by-products that kill microorganisms essential to plant growth. This is because the salts produced from chlorine react with hydroponic nutrient solution to create chlorinated hydrocarbons, a harmful toxin that kills plant cells.

Notably, sulfur or sulfate-rich water is also harmful as it produces hydrogen sulfide gas, which prevents plants’ oxygen absorption, resulting in a lack of energy. 

Introduce a fertigation system

Fertilizers in hydroponics are beneficial to plant development, but overuse can cause the build-up of salts or elements harmful to the roots. This kills the plant cells close to the root zone, thus limiting nutrient uptake. 

Introducing a fertigation system to the hydroponic system ensures that nutrients are dispersed evenly to all plant parts without causing toxicity or nutrient deficiencies. It also helps save on water usage by recycling excess water containing nutrients.

Clean the system regularly

Cleaning the hydroponic system is important because it prevents the build-up of harmful elements, by-products, and salts through your hydroponics medium.

Use a soft brush to scrub the reservoirs and planters to remove dirt, salt deposits, or any build-up. The best way to clean the system is by using a liquid or liquid-form algaecide solution, which can kill all types of algae and bacteria.

Ensuring proper pH management

pH plays a very important role in a hydroponics system because it affects nutrient uptake. The ideal range for most crops is between 5 to 6.5. 

Implementing proper pH management involves monitoring the nutrient solution in your hydroponics substrate. This ensures that it remains at its ideal range by adding or removing pH up/down solutions or adjusting with water treated with RO if necessary. 

Use pH test strips to check the pH level of your nutrient solution regularly and adjust accordingly using different pH balancing chemicals.

Proper EC regulation

Electrical conductivity (EC) is the concentration of soluble salts or ions in a solution. It’s measured using an EC meter which you can use to regulate nutrients properly. High EC levels cause leaf tip burn, while low EC levels cause slow growth.

While checking EC is expensive, high EC build-up is detectable using white vinegar, which turns cloudy when added to water with a high EC level. Use a conductivity probe or EC meter to determine the exact EC level of your water.

The best way to maintain proper EC levels is by adding nutrient additives to the nutrient solution in your hydroponics medium. This removes excessive salts. Chemical substances such as EDTA reduce the toxic build-up while hydrogen peroxide increases pH level for more effective nutrient absorption.

Hydroponic beds of cannabis seedlings
Hydroponic beds of cannabis seedlings

Get a hydroponic growing medium that meets your plant’s needs

The type of hydroponic medium you choose to use greatly determines the health of your crop. Take your time researching the different types of hydroponic media available in the market. Consider their pros and cons to ensure that you choose the best hydroponic growing medium for your plants. 

While most of these media can support multiple hydroponic systems, choosing one suitable for your setup is crucial. The right choice ensures you produce healthy, vigorous crops free of harmful toxins and salts.

Remember, using a non-nutritive medium is the best option to ensure proper pH management and nutrient absorption. The best hydroponic growing medium for cannabis should hold nutrients easily while preventing the build-up of harmful toxins, check-out our store.


About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.