How Aquaponics Functions

They say one person's discarded items can be another's treasure. The day-old bagels that a restaurant chain deems too stale for customers are seen as a perfect meal for the hungry when donated to a homeless shelter. The excitable puppy, once abandoned for chewing shoes, becomes a lively companion in a new family. What one group views as waste, another takes in as sustenance. It's a beautiful cycle.

With aquaponics, this cycle continues – though it has nothing to do with bagels or puppies. Aquaponics is a technique for growing both plants and fish in a managed setting. Fish are housed in tanks, and plants are grown hydroponically — without soil. The plants' roots hang into water-filled beds. As fish live in their tanks, their waste accumulates, becoming toxic to them. But what harms fish is beneficial to plants; they thrive on the nutrients found in fish waste. In an aquaponics system, the nutrient-rich water from the fish tanks is directed to the plants. The plants take in the nutrients, cleaning the water in the process. This purified water is then cycled back into the fish tanks.

This farming technique, which combines fish and crop production, offers multiple benefits. First, it eliminates the need for synthetic fertilizers and chemicals, as fish waste naturally fertilizes the crops. Second, it conserves water by recycling it within the system, rather than spraying it over fields. Third, aquaponics can be implemented anywhere, reducing the need for communities to import fish and produce from distant regions, thus saving on fuel – another positive impact.

Aquaponics, with its modern-sounding name, might appear to be a recent innovation by eco-conscious groups. However, its roots go back to ancient civilizations. The concept dates back to the Egyptians and Aztecs. The Aztecs, for example, created chinampas—artificial floating islands—where they cultivated crops like maize and squash. Fish lived in the surrounding canals, and their waste settled on the canal floors, providing natural fertilizer for the crops [source: Growfish]. Additionally, nations in Southeast Asia, such as Thailand and China, have utilized aquaponic methods for centuries in their rice paddies.

Now, let's explore how this ancient farming technique is being used in modern times.

Introduction to Aquaponics

Growing plants and fish through aquaponics is both environmentally friendly and cost-effective. These systems do not rely on chemicals and use only about 10% of the water typically required by traditional farming methods. Aquaponic systems are closed-loop, meaning once they are filled with water, only small amounts are added to replace what evaporates. But how is it possible for a water-based system to use less water than conventional farming?

The secret lies in the continuous recycling and reuse of water through natural biological processes. The fish waste creates bacteria that convert ammonia into nitrate. This nitrate is absorbed by the plants as a vital nutrient. The core idea behind aquaponics is turning waste into a resource.

Let’s break down the process step by step:

Since fish waste serves as a natural fertilizer, there's no need for chemical fertilizers. This saves both money and energy that would otherwise be spent on applying those chemicals. In fact, the only traditional farming task involved in an aquaponics system is feeding the fish.

Now that you understand how aquaponics functions on a biochemical level, let’s dive into which types of fish are most suitable for these systems and which plants flourish in them. Let’s explore.

Requirements for an Aquaponics System

A variety of warm-water and cold-water fish species have been adapted for aquaponics systems. The most commonly farmed fish in these systems include tilapia, cod, trout, perch, Arctic char, and bass. Of all these, tilapia is the most well-suited. They are highly resilient to varying water conditions, such as fluctuations in pH, temperature, oxygen levels, and dissolved solids. Additionally, tilapia are in high demand due to their popularity in both markets and restaurants as a white-fleshed fish.

Which plants thrive in aquaponics systems? This depends on the fish tank density and the nutrient composition of the fish waste. Generally, the best plants for aquaponics are leafy greens and herbs. The nitrogen-rich fertilizer produced from fish waste helps plants grow lush, vibrant foliage. As a result, leafy plants such as lettuce, spinach, chives, bok choy, basil, and watercress, which have low to medium nutritional requirements, tend to thrive in these systems.

Fruit-bearing plants have higher nutritional demands. While they can grow in aquaponic systems, they require tanks with higher fish density and established systems. Vegetables such as bell peppers, cucumbers, and tomatoes can be successfully cultivated in these systems. However, root vegetables like potatoes and carrots do not perform as well, as they become misshapen without soil and are difficult to harvest properly.

Water plays a crucial role in aquaponics, alongside the plants and fish. Monitoring the pH levels of the water, which determines its acidity, is essential for maintaining safe conditions for the fish. Water quality testing tools are vital to ensure both the fish and plants remain healthy. It's also necessary to track dissolved oxygen, carbon dioxide, ammonia, nitrate, nitrite, and chlorine levels. Factors like fish density, growth rate, and feed consumption can cause rapid changes in water quality, requiring close attention. While the ideal ratio of fish tank water to hydroponic beds varies by species and system, a general guideline is a 1:4 ratio—one part water and fish to four parts plants and growing medium.

Some aquaponics systems are equipped with biofilters, which use living materials to naturally filter pollutants and convert ammonia and other waste into nutrients. In other systems, fish waste is directed straight into hydroponic vegetable beds. Gravel in the beds acts as a bioreactor, facilitating the chemical processes needed by living organisms. It helps by removing dissolved solids and providing a surface for nitrifying bacteria to convert waste into plant nutrients.

Looking to grow food in your own backyard? Keep reading to find out how to set up an aquaponics system right at home.

Home Aquaponics

While aquaponic systems play a significant role in large-scale industrial food production, they can also be easily incorporated into backyard gardening. Whether you set up a system on your patio, apartment roof, or in your own backyard, a properly functioning aquaponics setup can provide enough food for your entire household.

Setting up a full-scale commercial aquaponics system can be expensive, but for backyard gardeners, it's possible to build an affordable system using recycled materials. Aquaponics offers numerous advantages for home vegetable gardeners. It uses much less water than traditional gardening, with minimal water loss due to evaporation. Your harvest will be organic, as no chemicals can be used—doing so would harm the fish. Additionally, vegetables grown in aquaponics systems grow much faster than in conventional gardens. For instance, cucumbers can be harvested in as little as 25 days after being transplanted from a traditional garden into an aquaponics system [source: Growfish].

What are the essential components you'll need to set up your own backyard food production system? The setup will vary greatly depending on the size and location of your system, but here are some of the must-have items to get you started:

Aquaponics is an environmentally friendly method of growing both fish and plants, whether on a small or large scale. For more details on other plant and gardening topics, check out the links provided on the following page.