An introduction to growing cannabis with aquaponics

What is aquaponics?

Aquaponics is a growing technique that combines two efficient systems: Aquaculture, a process of farming fish such as tilapia, koi, or bluegills, and hydroponics, a method of growing plants without soil. When the two are combined, you can create a nearly closed loop system that produces both plants and fish for consumption.

How do aquaponic systems work?

Aquaponic setups are very similar to hydroponic setups, but the source of nutrients for plants is different—nutrients come from the waste of the fish. The plant roots absorb the nutrients and then purify the water before nutrients are returned to the aquarium. Fish food is the only input you’ll need, and this can be grown or purchased.

The primary nutrient produced from fish waste is nitrogen with trace amounts of other minerals. Because of this, basic aquaponic systems are great for vegetative growth, but you’ll need to add additional nutrients like phosphorus and potassium for flowering. This can also be remedied with a double-root zone.

A double-root zone allows you to divide roots into two sections: The bottom half of the pot gets submerged in water, while the upper half of the pot can be filled with soil. This allows additional nutrients to be applied to the roots without contaminating the water. 

The two sections can be separated by burlap, which allows roots to travel through while preventing soil from reaching the water. When watering with additional nutrients, avoid oversaturating the soil to keep the water below in the aquaponics system clean.

Aquaponics vs. hydroponics for weed

Aquaponics utilizes a hydroponic setup for growing weed, with the addition of fish in the water chamber. This allows you to skip putting liquid nutrients in plants and instead rely on the waste of fish, a more natural source of nutrients.

The other main difference is the cultivation of fish in addition to cannabis.

Learn more about hydroponic setups here.

Best fish for growing cannabis with aquaponics

Some considerations before choosing fish for your aquaponic setup:

• Water temperature
• Tank size
• Maintenance difficulty
• Availability

Some fish need warmer water than others, so you may need to invest in a water heater or be sure your setup is in a warm place. Some fish are also bigger than others or more difficult to maintain, requiring more labor or money.

Here are types of fish most commonly found in aquaponic setups because of their low maintenance and versatility:

• Tilapia
• Trout
• Goldfish
• Catfish
• Koi

Advantages of growing weed with aquaponics

• Sustainability: Aquaponic systems use the waste of one organism to feed another. Fish food manufactured specifically for aquaponic systems ensures your plants will be free of toxins, and the plants will help fish grow strong and healthy. 
• Growth rate: Aquaponics is a great way to grow cannabis plants quickly. By allowing the roots to take in high levels of oxygen they are able to absorb more nutrients and will thrive.
• Water use: Aquaponics systems use considerably less water than traditional systems because they recirculate water.

Disadvantages of growing weed with aquaponics

• Initial costs: Setting up an aquaponic system is more costly than a soil or even hydroponic setup. 
• Maintenance: Fish need water in a specific temperature range, so you’ll need more equipment and resources to warm or cool water, and it will require more work to maintain.
• Algae: As with a hydroponic system, there’s a lot of moisture, requiring you to be on high-alert for algae growth that can harm your plants. Aquaponic systems require cleaning and sterilization to protect plants from algae.

Common challenges when growing weed with aquaponics

Growing weed in a hydroponic setup can be challenging enough, and growing in an aquaponic setup is even more difficult. Growing with aquaponics is not recommended for first-time growers.

Aquaponics can get complicated because you have two focuses: plants and fish, instead of just worrying about your weed plants.

As with growing in hydroponics, using water as your grow medium can be challenging and generally involves more equipment, time, and money.

A tricky thing with aquaponics is being able to balance the fertilizer from the fish that goes into your plants. If growing with aquaponics, be sure to have a firm grasp of nutrients and pH levels, and how to balance them.

How to set up an aquaponic weed garden

The easiest way to start an aquaponic setup is to repurpose an old fish tank and pump. Be sure to dechlorinate the water and allow it to cycle for 4-6 weeks before adding any fish.

Then you’ll need to create a media bed for the plants. Some growers use one big flood tray for a number of plants, and some use individual pots, as in the graphic above.

Then add the fish, and then the plants, and you’re ready to go! Just feed the fish to begin the cycle, and they will create fertilizer for the plants in no time.

Trevor Hennings contributed to this article.

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