Your choice of grow media will significantly impact the cost of building and maintaining your aquaponics system. But with so many types of grow media available, it is confusing to know what will work best for you. That is why this guide is written to help you understand what aquaponics grow media is, what are the available choices and what will work best for you.
What is Grow Media in Aquaponics
Aquaponics grow media is a natural or synthetic soilless material that supports the body of your plants. Like soil, it protects and ensures that plant roots are established in the right position. Grow media also serves as a surface area for bacteria to thrive inside the grow bed and acts as a filter for the solid waste expelled out of the fish tank and into the grow bed. However, it is important to note that not all aquaponics methods use aquaponics grow media, like the raft system and nutrient film technique (NFT) where the plants are grown in floating rafts and PVC pipes.
Factors to Consider in Choosing Aquaponics Grow Media
In choosing the suitable aquaponics grow media for your system, there are several options you can choose from. But for the success of your aquaponics system and in order to choose the right grow media for your system, there are several factors that you need to consider.
Too small grow media might clog your system. While too large grow, media might cause air gaps that can affect plant growth. The recommended grow media for aquaponics are ½" to ¾" in size, with an adequate surface area for colonizing bacteria.
Weight is an important factor in choosing your media. If you have smaller or flimsy aquaponics bed setups, see to it that your grow media is not too heavy or bulky. Your system might physically collapse if the structure cannot support the weight of your grow bed. Choose a grow media that is light to medium weight because if your grow media is too light, it might float and clog your system, and if it's too heavy, it might become unmanageable in the long run.
Monitoring and balancing your system's pH level is something you need to do regularly. The pH level of your system must be within the ideal range. That is why it is important to choose a grow media that is pH-neutral. Opting for a pH-neutral grow media will allow you to manage the pH level of your system better.
If you opt to use gravel or lava rock, it is good to do a test to see if they are pH neutral. To test, simply wash your grow media thoroughly with water, place it in a container, and then cover it with vinegar. If you see bubbles, then your grow media has a high pH. If there are no bubbles, it means your grow media is pH neutral.
Easy on the Hands
You will be handling the grow media with your hands when you place them in the grow bed and planting your vegetables. Sharp grow media can damage plant roots and can cut your hands as you tend your grow bed. So it is important to choose grow media that are safe and easy to handle.
If you are just starting aquaponics, you need to consider the cost. Grow media prices vary depending on what type of aquaponics grow media you'd like to use. For example, hydroton is expensive, while gravel tends to be cheaper. It is better to check your budget first and then choose the grow media that is within your budget.
Different Aquaponics Grow Media
Also known as clay pebbles, Hydroton is a (L.E.C.A.) Lightweight Expanded Clay Aggregate. Hydroton is one of the most expensive grow media in aquaponics, but they are an excellent option for growing any plants. They are lightweight but heavy enough to support the plant and full of microscopic holes that provide good drainage and increase the surface area and ensure plenty of nitrifying bacteria in your system.
Hydroton clay pellets are easy to maintain, porous, pH neutral, and reusable. Their porousness and shape ensure that there is a right balance of water and oxygen in the system. But they also tend to float when first used, which can potentially cause clogging in your pipes and filters, so be extra careful in using hydroton the first time.
Lava rock is widely used by many aquaponics growers as grow media because they are lightweight and have plenty of surface area. Lava rocks are typically pH neutral, porous, and provide good drainage and aeration to the system.
While lava rocks are a popular grow media option in aquaponics, it also has some downside. Lava rocks have sharp edges that might damage your plants' root system or cut your hands when you handle them.
Another great aquaponics grow media is the expanded shale. Expanded shales are porous, pH-neutral, and contain air pockets that provide additional surface area for bacteria. Because expanded shale underwent a heating process, their edges are slightly polished, so it's easy on the hand and will not harm your plants' root system. Expanded shale is reusable and more affordable than other types of grow media, so they are also a popular choice for aquaponics growers.
Gravel is the least expensive aquaponics grow media, but it's also one of the most problematic. Gravel does not hold water efficiently and has a lower surface area than other grow media, so it can be challenging to colonize bacteria. If you decide to use gravel, look for pea-size gravel that has been polished down to smooth out its rough texture. Lastly, always do a vinegar test on your gravel before using them in your system, as limestone is often present.
Growstones are a kiln-fired aggregate made from mixing recycled glass with calcium carbonate. They are lightweight, reusable, and porous like expanded clay, but shaped unevenly. Growstone provides adequate moisture and aeration to the root zone while their surface creates an ideal place for beneficial bacteria to colonize.
The downside of using grow stones as grow media is that there is some debate over whether grow stones can alter pH in an aquaponics system and they will break down over time.
Which Aquaponics Grow Media is Best for You?
In choosing the best aquaponics grow media for your system, bear in mind the factors you need to consider. Also, consider your system's size, budget, and availability of the grow media you want to use in your location. Make sure the one you choose has the ideal properties that are suitable for your system. If cost is not an issue, the best grow media to use is the expanded clay, but if you're on a tight budget, choose expanded shale or lava rocks.
Tips on Using Aquaponics Grow Media
Here are some tips that will help you in using and establishing grow media in your aquaponics system.
- If you're not using hydroton, it is best to test your grow media with vinegar before putting it in your system. Wash your grow media thoroughly with water and then place it in a container and pour enough vinegar. If you see bubbles, it means it has a high pH. Bubbles are the reaction of vinegar with limestone.
- Leave at least two inches of dry media to avoid algae growth. 12 inches is the recommended grow media depth, but you should add an extra two inches on top to prevent algae or fungal growth.
- Clean the grow media once a year to remove solids and other waste to avoid clogging your grow bed. A clogged grow bed can develop anaerobic zones that can kill the beneficial bacteria. A clogged grow bed will also reduce the nitrification process and will raise the pH in your system. A high pH level is an indicator of a clogged grow bed.
Thanks for reading! We hope this article guides you in choosing the right grow media for your aquaponics system. If you have experiences in using any grow media which can give valuable information and knowledge to others who are looking for the right aquaponics grow media, feel free to share them in the comment section below. For more aquaponics information, read our Ultimate Aquaponics Beginner's Guide.