Could Aquaponics Work on Your Farm?
Updated: May 28, 2020
With aquaponics you can simultaneously raise fish and grow plants, year round, in any climate. It’s sustainable, uses less water than conventional plant and fish production, and can produce high yields. Plus it requires no weeding.
Could aquaponics be a good addition to your farm? Here are some considerations and resources to help you make that decision.
Aquaponics vs. Aquaculture
It’s easy to confuse the two A-words, so let’s cover some terminology. Growing plants without soil is called hydroponics. Raising fish in an artificial environment is called aquaculture. Aquaponics is the integration of the two.
Hydroponic plant growers require nutrient-rich water. Aquaculture fish producers need to dispose of nutrient-rich water. Combining these systems is a brilliant and efficient idea. So much so that nature has used it ever since the first fish. Or the first fish egg.
How it Works
In addition to plants and fish, the third required component of aquaponics is bacteria.
The primary input in aquaponics is fish food. Fish eat the food then produce urine (containing ammonia, which in quantity is toxic to fish and plants) and fecal matter. Heterotrophic bacteria consume the fecal matter, excess food, and decaying plants to produce more ammonia as well as other compounds.
In addition, bacteria convert ammonia to nitrite (NO2), and then to nitrate (NO3), which plants consume. Bacteria will naturally attach to the tank and its contents when ammonia and nitrite appear.
Simplified, it looks like this:
You feed the fish
The fish make waste
Bacteria convert the waste to nutrients
Plants use the nutrients to grow (plus they filter the water)
Sounds easy, right? Well, part of the trick is making the right fish/plant choices. It is essential that you select a combination that shares similar requirements in terms of temperature, pH levels, and other factors.
Choosing Your Fish
Fish frequently chosen for aquaponic systems include bass, bluegill/sunfish/crappie, catfish, goldfish, koi/carp, pacu, salmon, perch, tilapia, trout, and others.
Among your first considerations when choosing fish are water temperature, pH range, and water quality requirements that are in line with your intended plants.
Fish heartiness is another big factor. Trout are great-tasting and do well in colder water, but they require more careful monitoring and control of pH and dissolved oxygen levels. Salmon are similarly tricky as they are less disease-resistant than other species.
Breeding habits and speed of growth are important considerations, too. However, keep in mind that faster isn’t always better, especially if you have a small tank. What fish are available – and legal – in your area will also be a factor.
Eating is a big consideration, both for people and fish. This includes what food your fish will eat, whether your fish will eat each other, and whether or not anyone will want to eat the fish. Ornamental fish are popular in aquaponic systems, but some, like goldfish, cannot be eaten.
Tilapia are near the top of these and many other lists, as they are a hearty, great tasting species that reproduce quickly and don’t eat other fish. They do require warmer water, however, and this can increase costs in colder climates.
Bluegill are similarly tasty and hearty, and can tolerate colder water. What’s more, throughout North America bluegill are easily caught and can be transferred to an aquaponic system. They can be cannibalistic, however, when breeding.
While nearly any plant can be grown aquaponically, best results occur when plants are chosen in tandem with fish to ensure they both thrive in the same environment. To compare plant options, both fish resources listed above also have plant sections, as does aquaponics.com.
All three resources cite leafy lettuces as among the most robust and marketable plant choices. In addition to lettuces, kale, Swiss chard, and watercress also thrive readily. Other popular choices that may be better suited to more established systems include cauliflower, cucumbers, peppers, strawberries, and tomatoes. Keep in mind that many non-edible plant options, including ornamental flowers, are also frequently chosen for aquaponics.
Looking for a recommendation of a proven approach? Lettuce and tilapia are a very popular combination for both home and commercial aquaponic systems.
Many of the same factors you use to choose food for other livestock (or for your family) apply to fish as well. Will you choose organic? Will you select only non-GMO options? Will you try to avoid fish meal in the name of sustainability, even if others report that their tilapia grows best on fish meal diets?
Beyond these preferences, the fish you choose will play a role in the food you select. You can select species that are carnivores, detritivores, herbivores, or omnivores. Fish that require high protein diets will be more expensive to feed. Choosing carnivorous fish can be costly when they eat each other. As you might expect, omnivorous fish are easy to feed. Accordingly, you should consider food choice when selecting fish.
In addition, it’s important to note that cheap food can negatively impact water quality and increase filtration needs by producing additional wastes.
Three Kinds of Aquaponic Systems
Another point to consider when choosing plants is compatibility between each plant and the type of aquaponic system you’ll use. There are three main types; media bed, nutrient film technique, and raft.
In a media-based system, plants are grown in a media like gravel or clay pebbles, which help to filter waste. Also known as “flood and drain” systems, they are the most commonly used aquaponic system, and are compatible with both small plants and larger fruiting varieties.
While they are easy and inexpensive to set up, media systems are difficult to scale into commercial use.
Nutrient Film Technique (NFT)
In a NFT system, plants are grown in a long channel in which water flows continuously in a very thin film. Once water reaches the end of the channel it is redirected to the fish tank.
Because these channels can be stacked, this type of system can be easily accessed and can make very efficient use of vertical space.
NFT systems work best with greens that have smaller root systems.
Raft or Deep Water Culture (DWC)
In a raft or DWC system, plants are grown on (polystyrene or foam boards) that float on the water.
Raft systems require much more water, which in turn makes them more stable: large fluctuations in nutrients and temperature are less likely. For this reason they are common in commercial usage, despite having increased filtration demands. Raft systems are ideally suited for smaller leafy plants like lettuce.
A more detailed comparison of all three systems can be seen at ecolifeconservation.org.
What Equipment Is Necessary?
First you need some place to put everything.
Allen Pattillo and the University of Iowa created an informative series of videos on aquaponics. In “Everything You Need to Know About Aquaponics,” Allen indicates that the decision of what kind of building works best for aquaponics depends on whether it is easier for you to produce light or heat.
If light is more costly where you live, you may choose to grow in a greenhouse. This is also a great option if you already have a greenhouse. On the other hand, if it’s cheaper for you to produce light, then growing in a warehouse with artificial light might be the best choice for you.
If you choose to grow in a warehouse, you will need to shop for lights. If so, advancements in LED technology are continually bringing more efficient options to market.
In addition to a structure and light, required equipment include fish tanks, filters, and pumps.
Fish tanks are available in a variety of shapes and sizes, and in a wide range of prices. In terms of shape, round tanks offer better circulation than square or rectangular options. Tanks that result in more water surface area will produce more oxygen; short and wide being preferred over tall and narrow.
Keep in mind that larger tanks not only facilitate growing larger fish (and support species that require more space), but also reduce fluctuations in temperature and pH levels, producing a more stable environment.
Make certain that your tanks, or whatever they are lined in, are food safe. Both metal and plastic can introduce toxins into your system, so this is an important point.
Solid Waste Filters
In addition to bacteria naturally transferring ammonia into nitrate, you will also have to actively deal with solid wastes. There are three kinds of solid wastes in an aquaponic system: settable, suspended, and floating solids.
As the name suggests, settable solids settle to the bottom, where they can be collected by a swirl filter, radial flow filter, or a clarifier.
Suspended solids are more difficult to collect and are more prevalent in DWC and NFT systems. Common solutions include bird netting, and screen or drum filtration.
Floating solids need to be broken down, likely turning into suspended solids. This may be accomplished using the return line of your pump.
Addition information on various solid waste filters can be found at howtoaquaponic.com.
The water in your tank needs to be recirculated between 1 and 3 times every hour. The capacity of your tank is a primary factor in choosing an appropriate pump. Also important is how much elevation difference there is between your pump and where the water needs to go.
Consider these three pump types:
Submerged pumps are cheap and easy to install, but can create unwanted heat and are less efficient, especially problematic in larger tanks.
An inline pump is more labor-intensive to install, and is noisier.
Airlift pumps use compressed air to move water. They are typically not submerged and tend to not be as efficient in larger tanks.
Another factor is efficiency. Buying a more expensive pump that requires less electricity to run may pay for itself quickly. It’s important to remember that electricity, both for pumps and growing lights (when applicable), make up a significant part of your operating cost.
Finally, don’t confuse water pumps, or airlift pumps, with an air pump. An air pump is another vital item on your list: this is how you manage dissolved oxygen in your system.
Continuously producing healthy plants – and fish – all year round in any climate is a pretty exciting thought, particularly to those of use in the colder latitudes. Like so many endeavors, adventures in aquaponics are highly scalable, so you may choose to simply start small to see if aquaponics might be a good fit for you. I hope this post inspires you to learn more.
Aquaponics – National Agricultural Library, U.S. Department of Agriculture
Best Aquaponic Fish Tanks – greenandvibrant.com
Go Green Aquaponics Blog – gogreenaquaponics.com
Seven Rules-of-thumb to Follow in Aquaponics – The Food and Agriculture Organization
UKNOW: Aquaponics" Video Series – Iowa State University Extension
What is Aquaponics? – howtoaquaponic.com
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