Photography by Connor Fyfe for Herb
Aquaponics is probably the coolest way you can grow weed, and also the most self-sustaining system—once it is carefully calibrated. This system grows fish and plant-life in such a way that allows both to support each other’s growth, with minimal intervention from the grower.
Here’s how it all works. Fish are housed in an aquarium which is connected, via a pump system, to a separate tank which holds the water and nutrients necessary for the plants to grow. The nutrients come from the waste produced by the fish and the plants, in turn, filter the water which is then pumped back into the aquarium. A perfect closed loop.
This form of growing, known as Aquaculture, was first put into practice by Dr. James Rakocy of the University of the Virgin Islands. Dr. Rakocy’s discovery emerged from his experiments to find a natural way to filter water in an aquarium. He began by using plant life naturally found in aquatic areas, but eventually realized the potential for a multipurpose system, which could grow edible plants like lettuce.
In the 1990s, Missouri farmers Tom and Paula Speraneo made modifications which would allow the system to grow a wider range of plant-life by adding growing media, like soil, to the system, and laying the groundwork for aquaponics as a method of growing cannabis.
The waste produced by fish provides one of the most important nutrients for plant growth: Nitrogen. That’s why aquaponics systems are ideal for growing simple plants like lettuce and herbs, which can float freely in the system’s reservoir. Cannabis plants, however, require a few small additions to the aquaponic system to provide the full NPK range of Nitrogen, Phosphorous, and Potassium. This modification simply involves the addition of growing mediums like soil and rockwool.
Pots are placed on a growing tray and filled with a growing medium, like rockwool, which will allow the roots to grow down through the bottom of the pot and into the nutrient-rich water in the reservoir below. Soil is also used as a top layer in the pot, separated from the rockwool by a thin layer of burlap, which prevents the soil from contaminating the water while also allowing the roots to grow through it. This modification is known as a double-root zone, because one section of the roots are able to access the nutrients in the soil while the other reaches down through the pots to access the nutrient-rich water.
For beginners, this system can be pretty expensive and complicated to achieve at home, as its initial stages require a lot of setup and calibration. If you already have some experience with hydroponics and the equipment necessary for a hydro grow, however, you are well on your way to an aquaponic system. The addition of marine life may require a bit of research and extra work, but if you’re looking for a challenge, the extra effort is worth the time and energy you’ll save once the system is fully functioning.
It is important to remember that this grow method sustains two kinds of life, and is essentially a condensed ecosystem. As a result, choosing high-quality pipes and filtration systems would be a wise investment—the money you lay out initially will be recouped over time.
It will also take time and a bit of effort up front to reach the point at which this system is entirely self-sustaining. Growers will have to go through the trial and error process of figuring out the ideal fish-to-plant-ratio and feeding regimen for the fish to ensure that the plants have adequate nutrients, and the water is effectively filtered for the fish.
As discussed, when it comes to nutrients, cannabis plants are a little more complicated than simple non-flowering herbs. They require different combinations of nutrients at the flowering stage than they do at the vegetative stage. This is why some aquaponic growers suggest setting up two separate tanks for both stages.
Alternatively, you can manually add the additional nutrients required at different stages. You will have to ensure that you do so without harming the fish, however. If adding additional nutrients, be sure to test the water to ensure that you are adding only as much as your plants can consume to make sure that the water that reaches the fish is effectively filtered.
Some additives that growers like to supplement their systems with are calcium hydroxide and bicarbonate, to make up for a lack of potassium and calcium in the system. Some also suggest the use of seaweed-based potassium nutrients to supplement your plants while causing no harm to the fish.
One of the most efficient options, recommended by Sylvia Bernstein, author of Aquaponic Gardening: A Step by Step Guide to Growing Fish and Vegetables, is to add worms to the soil of your aquaponics system. A process known as vermicompost, the addition of worms can provide natural nutrients, and even break down some of the solid waste produced by fish to speed up the bacterial process of converting that waste to nutrients. Red wiggler composting worms–not earthworms–are considered ideal for this.
An aquaponics system can support pretty much any form of marine life that can survive in a freshwater aquarium. This includes shellfish and prawn, but keep in mind that different marine life may produce different levels of the nutrients needed to keep your plants fed, altering the plant-to-fish ratio.
Most growers prefer to use fish like Tilapia which are both edible and can thrive in crowded waters. If you’re only looking to harvest the buds from this grow, you can easily use goldfish or koi as well.
Some of the most common fish that are used in an aquaponics system include: Catfish, Tilapia, Goldfish, Trout, Koi and Blue Gill.
One of the most important things you will need for aquaponics system is patience. That is especially true when it comes to bacteria, which are vital for the survival of an aquaponics system, and something which hydroponic growers may need to get used to. “Bacteria is a bad word in the hydroponic world,” Bernstein tells Jill Cloutier in her podcast A Sustainable World. “It’s a really good word in the aquaponic world.”
Nitrifying bacteria are a vital component of the aquaponics set up. These bacteria convert fish waste into nutrients, which your plants can use, and filter the water of ammonia so that marine life can survive. But developing a colony of bacteria can take time if you’re starting your system from the scratch—waiting for full colony form can take up to 6 months. That said, it’s possible to speed up the process and prevent the need to supplement your system with additional nutrients while you wait.
Nitrifying bacteria that convert fish waste into plant food are naturally occurring and will eventually colonize the system through a process called cycling, which can be sped up by introducing some of that bacteria manually.
To do this you could find commercially available sources, but Bernstein also suggests finding a friend who has an aquarium, finding similar bacteria growing in the sponge from the aquarium’s filter or using the slime that grows on rocks in a nearby lake or pond.
Setting up an aquaponics system can take time and a lot of research, which is likely the reason that they are some of the rarest cannabis grow-ops around. Yet this system can also be the most rewarding and least labor-intensive way to grow cannabis once set up. For more information check out Aquaponic Gardening: A Step by Step Guide to Growing Fish and Vegetables.