The Magic Behind Aquaponics: And Why it Isn’t Really Magic

by Lexi Harder


I’ve been working at Oko Farms, New York City’s largest and oldest aquaponics farm, since the spring of 2016. And in those two years, I’ve probably explained what it is I do every day about a hundred times to new acquaintances and people who come to the farm to learn. My explanation has gotten simpler and simpler — “I grow plants and fish together in a recirculating ecosystem” — and while it gets the point across, it doesn’t really explain exactly what aquaponics is, and why it’s so special.

The Basic Science Behind Aquaponics

The first thing people usually ask me after I tell them what I do is: “isn’t that just hydroponics?” It’s true, hydroponics and aquaponics both involve growing plants not in soil but in water. Where hydroponics requires special fertilizers to be added to pure water in order to provide essential nutrients to plants, aquaponics relies on fish waste to do the job instead. The etymology behind the word “aquaponics” explains what it is, by uniting “aqua” from “aquaculture” (the practice of raising fish) and “ponics” from “hydroponics.”

In very simple terms, aquaponics works because the fish and plants are both providing services for each other, the way they do in natural ecosystems like in oceans, rivers and lakes. Fish create waste which is then in turn used as food for plants. By taking up fish waste, the plants clean and filter the water for the fish, keeping their environment safe to live in. In this system, neither the fish nor plants can thrive without the other.

For laymen, my explanation of aquaponics stops there. But the aquaponics cycle depends on a third party, which is the presence of beneficial bacteria in the water. These bacteria, most often attributed as nitrosonomas, nitrobacter and nitrospira, are the crucial link between the creation of fish waste and the plants’ ability to absorb the waste as nutrients. When fish create waste, it is in the form of ammonia, a chemical compound that is highly toxic to fish, and unable, for the most part, to be absorbed by plants. What the bacteria do is consume ammonia, and convert it into nitrates, which plants use to form their leaves and stems and perform photosynthesis. This process is more broadly known as the nitrogen cycle and also takes place in nature and in organic soil farming.

To review, aquaponics is a relationship between fish, bacteria and plants, wherein all entities perform essential services for each other. The fish create waste, the bacteria convert the waste into nutrients and the plants take up the nutrients, cleaning the water for the fish.

Why Aquaponics?

Don’t Forget the Water

So, why is aquaponics better than hydroponics or aquaculture alone? After all, it seems like a lot of work to learn how to grow plants in water and learn how to raise fish. It’s obvious to me because I experience it first hand, but perhaps the most amazing aspect of growing aquaponically is that, if executed correctly, the water in any given aquaponics system never, ever has to be thrown out. Because aquaponics is a self-fertilizing form of farming, getting rid of the water is actually detrimental to the health of the system as a whole. In fact, as the years go by and a given system’s bacterial colony becomes more established, the scope of what can be grown increases from greens to fruiting plants.

To contrast, hydroponics systems require water to be replaced when minerals build up from continued application of liquid fertilizers. In aquaculture, overstocked fish farms must replace their water on a daily basis to mitigate the effects of fish waste buildup. In fact, in 2010 the United States aquaculture industry withdrew almost ten thousand million gallons per day (Mgal/d). And of course, Ecocentric readers know that conventional soil agriculture is a huge environmental problem from a water usage standpoint. Not only because it’s unsustainable in times of drought, but also because runoff of chemical fertilizer into natural water systems is a leading cause of harmful algae blooms and dead zones.

At Oko Farms, the body of water in our system has remained the same since 2013, when the farm was constructed. We never remove existing water, and only replace what water the plants take up or what we lose to evaporation in the hot summer months. And because Oko Farms is an outdoor space, rainwater usually takes care of all of our water needs. In 2017, we supplemented our aquaponics system with municipal water only twice.

Aquaponics Applications — The Sky is The Limit

Although aquaponics is an ancient form of farming, the aquaponics industry today is still in its infancy. But people all over the world are recognizing the possibilities for applications, from providing a local source of food to urban areas with toxic soil and limited access to water, to being a perfect classroom example of how ecological farming can work. And in a time when fish fraud is at an all time high, it’s a way for home aquaponics practitioners to take control over where their fish comes from.

Are you interested in learning more about aquaponics? A good place to start is my blogs on FoodPrint — and you can check out my post on aquaponics resources to find out where you can learn more from the experts.

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