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Aquaponics is a gardening method that leverages the symbiotic relationship between fish and plants. The two grow together with the plants naturally filtering water for the fish and the fish providing an organic food source for the plants. Learn more about this farming method that has made its way into home gardening.
What is Aquaponics?
Simply put, aquaponics is a combination of aquaculture (raising fish) and hydroponics (growing plants in water). Aquaponics combines these practices into one system, creating a less wasteful setup for growing both fish and plants.
By adding a fish tank into your hydroponic growing system, you can stop using the fertilizers needed for hydroponics and you gain another edible crop—the fish! Both the plants and the fish benefit from this symbiotic relationship. In combining both hydroponic and aquaculture systems, aquaponics capitalizes on their benefits, and eliminates the drawbacks of each.
Many different varieties of fish have been shown to grow well in aquaponic setups, including tilapia, bass, trout, perch, and horned pout/catfish. These fish do get fairly large, so you will need a significant amount of space to grow fish for consumption. If you can't dedicate that much room but still want to try your hand at aquaponics, goldfish make for a great substitute, though they'll be a pet rather than a food item!
Lettuce grown in a floating raft system. Photo by poramesstock/Shutterstock.
No matter which fish you keep, there are a multitude of plants that can be grown in an aquaponic setup: tomatoes, peppers, lettuce, chard, basil, and even strawberries—giving you enough for a full salad, dessert included.
Of course, there are downsides to aquaponics. As mentioned above, you need a lot of space to raise edible fish (containers are usually hundreds of gallons in size), as opposed to simple hydroponics, which can be done in a 10-gallon tub. Additionally, aquaponic systems cost more to set up and maintain, since you'll need to buy fish and a constant supply of fish food. It can also be a lot trickier to make sure that the water's pH and nutrient levels are kept within an acceptable range for both the fish and the plants.
Drawbacks aside, if you've had experience and success with a hydroponics setup, dive into something new and give aquaponics a try!
Unlike hydroponic setups, where the plants may be grown directly in the nutrient-rich water, aquaponic systems generally require that you have two separate containers connected by pumps and hoses. This is done to prevent the fish from nibbling on the plants' roots, and to provide proper circulation, aeration, and filtration of the water.
Two types of hydroponic growing systems can easily be modified to include fish:
Media-Based Ebb & Flow System
In this system, plants are grown in a tray of inert growing medium (such as pea gravel), which is connected to a separate container that houses the fish. Water from the fish tank is pumped through the plant tray, where it is cleaned and aerated as it runs through the inert growing medium that holds the plants in place. The filtered water then runs back into the fish tank to repeat the cycle. (Typically, the plant tray is suspended above the fish tank, allowing the filtered water to drip back into the tank.)
Nutrients for your plants come from fish waste products. Uneaten fish food, fish poop, and ammonia produced by the fish are filtered from the water and converted to plant food by beneficial microbes present in the growing media.
Pea gravel has been shown to do a good job of not only anchoring the plants, but also supporting the two strains of microbes responsible for processing the waste and providing trace amounts of calcium for the fish. After passing through the plant tray, clean water gets oxygenated as it rains back down into the fish tank.
No space for big fish? Try aquaponics with goldfish instead!
Floating Raft System
In this setup, styrofoam sheets float on the surface of the water in the plant container. Holes cut in the styrofoam support net pots filled with an inert growing medium (such as perlite) that dangle over the water. The plants grow with their roots hanging into the water, which is pumped from the tank where the fish live.
In this setup, it's necessary to use an airstone to oxygenate the water for both the fish and the plants, since the plants' roots grow directly into the water and aren't exposed to air. As the water exits the plant container, it should be run through a filter to clean it thoroughly before it is pumped back to the fish tank, where the cycle begins again.
Other Aquaponic Setups
There are many different plans for aquaponic growing systems available online. Google “barrelponics” for plans to make one using recycled plastic barrels, or check out a premade aquaponics kit, such as this one from Back to the Roots.
Whatever type of system you use, it is important not to overfeed the fish. They should be able to clean up their food in 15 minutes. It's better to feed them small meals 2-3 times a day rather than all at once. Check your fish and plants daily. Remember that you are trying to create a healthy little ecosystem and it needs tending to succeed!