by Nebula Haze
Table of Contents
In order to get high yields with aquaponics, a cannabis grower needs to familiarize themselves with the basics of how an aquaponic system works. To grow cannabis successfully in aquaponics, the system must be configured to produce the high levels of nutrients needed by a plant like marijuana, and that takes a little extra know-how!
Aquaponics is the art of combining aquaculture (growing fish in tanks) with hydroponics (growing plants in water). It’s sort of like organic hydroponics!
In an aquaponic growing system, fish are raised in a tank and the nutrients they produce (contained in their poop and produced by their gills) gets converted by bacteria into nutrients for the plants. The plant roots help clean the water before it is re-circulated back to the fish tank, completing the cycle.
Aquaponics creates a tiny ecosystem – fish make nutrients for cannabis while cannabis cleans the water for the fish!
Although fish are the most common species used for aquaponics, other aquatic creatures like shrimp, crayfish or prawns can also be used. Both edible fish and ornamental fish can be used successfully in an aquaponic system. Generally you want to pick a species that is hardy and can tolerate crowding. Tilapia is an edible fish that adapt very well to aquaponics, and koi or goldfish are great choices for ornamental fish since they are nice to look at and can thrive in sub-optimal environments.
Aquaponics may be the most efficient way there is to cultivate both fish and plants at the same time because combining them together reduces the cost of farming each one individually! In big commercial operations, aquaponics is used to produce profitable combinations like tilapia fish and lettuce. In smaller setups, aquaponics is a sustainable, low-technology and efficient way to create food even with infertile land and low resources – aquaponics dramatically reduces the amount of water needed for raising fish, while producing high-nutrient plants at the same time!
You feed the fish, they feed the cannabis!
When it comes to growing cannabis in aquaponics, one of the big goals is to set up a system that produces high levels of available nutrients. Growing cannabis plants gobble up nutrients, especially in the flowering stage, so you need to ramp up an aquaponics system to optimize it for high nutrient output! That means that you need to make sure you have a high density of fish, as well as a really great bacterial colony to convert all that fish poop into nutrients for your plants!
The Rearing Tank / Aquarium is where the fish or other aquatic creatures live. These creatures produce waste containing nutrients that are vital for plant growth. Common fish used in aquaponics include tilapia, koi and goldfish, but there are many other hardy species that can adapt to an aquaponic environment including blue gill and catfish.
Your system will have a Hydroponic Sub-System, which is basically the tank or reservoir where cannabis plants grow with their roots in the water. In many ways, you grow your cannabis plants in aquaponics just like you would with a traditional DWC/hydro setup. The main difference is the fish produce nutrients instead of you having to add them!
Bacteria make up your Biofilter, the “heart” of your aquaponics system. The bacteria biofilter is the missing piece that allows you to run a symbiotic relationship between the fish and the plants like in nature. When you create a nice home for the bacteria, they work hard to convert fish waste into usable nutrients for the plants. The biofilter can be its own separate component in the system, or you can cultivate a biofilm of bacteria inside the actual fish tanks and hydroponic reservoirs. Without a colony of bacteria, your plants will be unable to use the nutrients in the water from the fish (and fish will die from too-high levels of ammonia)!
The Secret to Success with Marijuana & Aquaponics is Patience
The secret to any successful aquaponics system is patience! You need to create a balance between the fish, bacteria and plants, and this takes time. Unfortunately, there’s not necessarily a lot of ways to speed things up while your bacteria is being colonized.
It’s like growing a cannabis plant in a way, you can do things to get the plant to grow faster, but no matter what you’re still going to have to wait for the plant to grow until you get to harvest. You can help your bacteria grow, but they need time to build up their numbers and form a robust colony.
That means in a young/new aquaponics tank you have to spend time cultivating your bacteria, and in the meantime you may have a lot of adjusting to do to maintain a balance that will keep both plants and fish alive: adding nutrients, changing the water, testing nutrient levels, managing pH and possibly adding/removing fish.
But as you create more of a balance, and your tank becomes more mature, you will have a lot less to do. In fact, over time you can set the system to do most of the maintenance by itself!
1.) Cannabis Has High Nutrient Needs
Growing cannabis in aquaponics is similar to hydroponics, except fish and bacteria make the food! Your plants can’t use nutrients directly from the fish. Fish waste actually has to be converted to a usable form by the bacteria in your biofilter. Building a robust colony of bacteria for your biofilter can take 6 months or more, which means that additional nutrient supplementation by natural sources will likely be needed to grow a cannabis plant in aquaponics for the first few months.
The appetite of a cannabis plant for nutrients is especially voracious during the budding/flowering stage. When your plant is making buds, it’s sucking up nutrients like there’s no tomorrow! Fruiting plants with similarly high nutrient needs to cannabis (like tomatoes) have been successfully grown in aquaponics, but it’s much less common than growing something with simple and low nutrient needs like lettuce or herbs.
While “getting your feet wet” with aquaponics, don’t beat yourself up if you run into nutrient problems!
2.) May Need Separate Vegetative & Flowering Chambers
Vegetative and flowering cannabis have different nutrient needs for the best growth. So in order to completely optimize an aquaponic system for cannabis it may be necessary to maintain different tanks.
It may be possible to simply supplement your tank with extra nutrients during the flowering stage, but it can be harmful to fish to add an excessive amount of extra nutrients unless the plants use most of it up before the water is re-circulated back to the rearing tank! Extra planning and water testing may be needed to manage which nutrients are currently available.
3.) What to Do with Extra Fish
Aquaponics is spectacular at producing fish and plants at the same time. If a cannabis grower would like a constant supply of fish to eat or sell, an aquaponic system simply can’t be beat!
But if a cannabis grower does not want to actually harvest their fish, they need to plan on what to do with the extra fish as they die and need to be replaced. In order to maintain the equilibrium of your aquaponics system, it’s a good idea to regularly be adding new young fish as old ones mature and die.
How to Produce the Nutrients Needed by Cannabis
Even after your biofilter is established, you may still need to supplement with extra calcium, iron, potassium and possibly phosphorus to keep up with the needs of your cannabis, especially during the flowering stage.
Luckily there are natural sources to get extra nutrient supplementation without seriously affecting your fish. For example Maxicrop is a common nutrient additive made out of seaweed that works well in an aquaponics system to add potassium and trace minerals without hurting your fish.
Other common additives include cycling calcium hydroxide (hydrated lime or builder’s lime) and potassium carbonate (bicarbonate), which add calcium and potassium to the system while also raising the pH (since low pH is common in an aquaponics system that’s not well-established).
No matter what, when dialing in your aquaponic system it’s important to test your water throughout the process to see what nutrients are currently available. This lets you know where you’re running into nutrient problems, and also will help you know what to do to fix it. Not only will this help you take better care of your plants, it will also help you take better care of your fish!
Want to create a complete ecosystem with basically no input from you?
Some growers will introduce a worm farm (vermicompost) to the system to supplement nutrients naturally while breaking down the solid waste from fish which can’t be processed by bacteria. This is one way to actually “complete” the cycle inside the system.
Normally in aquaponics, these extra solids are filtered out and thrown away, but worms can liquefy it while providing an extra source of nutrients that can help bridge the nutrient gap and make sure cannabis is getting everything it needs without any extra supplementation.
At this point your main input into the system would just be fish feed. If you want to get even more sustainable, you could grow duckweed or another plant that fish eat and you wouldn’t even have to buy fish feed anymore! As the system gets more and more balanced, nearly all the energy input to the system can come from the sun or grow lights, producing a food/plant generating machine!
Ready to start growing cannabis with aquaponics? The following incredibly high-rated book will teach you everything you need to know so you can get started today!
Learn how to grow cannabis with aquaponics with Aquaponics Gardening: A Step-By-Step Guide to Raising Vegetables and Fish Together available on Amazon!
By following the tutorials and setting up your system to grow high-nutrient, flowering plants plants like tomatoes or corn, you will be giving your cannabis plants everything they need to succeed!