Aquaponics made Easy to Understand | How do aquaponics work?

Farming practices in the modern-day world are considerably different from those of decades ago. With the changes in climate, farming spaces, and tech advancements, fields such as aquaponics have continued to gain popularity. Basically, aquaponics is a combination of aquaculture and hydroponics. The former deals with the rearing of fish and other aquatic creatures, while the latter focuses on soilless plant growing. Ideally, an aquaponics system should sustain itself through the symbiotic relationship between fish and plants. So, how does aquaponics work? This guide will look at the basics, requirements, types, and benefits of an aquaponics system.

What is Aquaponics?

As other sectors make technological advancements to enhance productivity, agriculture has not been left behind. Over the past few decades, numerous farmers worldwide have taken an interest in hydroponics, the science of soilless farming, and aquaculture. In more recent years, though, a merge in these two fields led to the field of aquaponics, a science that combines aquaculture and hydroponics. Ideally, an aquaponics garden mimics the natural ecosystems found in rivers and lakes.

An aquaponics garden is based on the self-sustaining relationship between plants, nutrients, bacteria, aquatic creatures, and water. Taking a few cues from nature, an aquaponics system integrates several components. The waste products from fish serve as food for bacteria, converting them to plant nutrients. On the other hand, the plants clean the water, making it safe for the fish to thrive in, similar to what happens in natural aquatic habitats.

In most aquaponic systems, water from the aquaculture section is fed to the hydroponic section using a pump. Nitrifying bacteria found in the hydroponic section break down the fish waste into nitrates that are beneficial to plants. The clean water is then recirculated to the aquaculture section of the system. Keep in mind that the system barely loses any water to seepage and evaporation. Additionally, the water is continuously available to all plants whose roots remain suspended in water.

Aquaponics systems come in various configurations, all of which have immense benefits over traditional gardening methods.

Aquaponics Basics

Here is a look at some basic concepts surrounding the field of aquaponics.

The Importance of Fish

The aquaponics cycle starts with fish food being introduced into the system. When the fish consume this food, they process it and output fecal matter and urine, both rich in ammonia. Keep in mind that ammonia can be quite toxic to plants and fish. However, this fish waste is extremely important to keep the aquaponics garden running, and without it, the entire system would fail. The excreted urine and fecal matter, uneaten food, and decayed plant matter are then fed into a biofilter.

The Importance of Bacteria

Once in the biofilter, nitrifying bacteria act on the waste and break it down into nitrates essential for plant growth. Without the bacteria, the waste would accumulate in the water, adversely affecting the plants and fish. It would only be a matter of time before the entire aquaponics system collapses. Once the bacteria have broken down the waste into nitrates, it is up to the hydroponic system plants to keep the system going.

The Importance of Plants

The nitrifying bacteria break down harmful ammonia-rich waste into useful nitrates. However, since the fish do not need nitrates in the water, the plants absorb them in the form of nutrients. This results in sustained plant growth, and since there is no soil, absorption is extremely efficient. Once the nitrates are absorbed, the water is recirculated back to the aquaculture section, this time free of any harmful ammonia. The process starts all over again.

Use of Organic Pesticides

It is worth noting that the use of conventional pesticides can harm the aquaculture section of the system. To ensure the relationship between fish and plants remains unaffected, it is advisable to use organic pesticides, biological controls, such as ladybugs to control aphids, physical barriers, or other non-chemical traps.

Understanding Nitrification

Nitrification is the entire process that takes place during the conversion of organic matter and fish waste into plant-usable nutrients. Also known as the nitrogen cycle, it can be somewhat intricate but worth learning for any aspiring or existing aquaponics gardener. Fish in the aquaculture section excrete ammonia through their gills. Additionally, uneaten food can decay and produce ammonia that also goes into the aquaponics system.

Ammonia is harmful to plants and fish in its basic form but is extremely nitrogen-rich, which makes it potentially beneficial for plants.

Two bacteria types are responsible for the conversion. The first type converts ammonia into nitrites which are still not used to plants and, at some level, toxic to fish. The second bacteria type converts nitrites into nitrates, a form beneficial to plants. Where do the bacteria come from? Well, they occur naturally in any aquaponics system and multiply as the system requires. At times, the bacteria can be manually introduced into the system. In some large-scale aquaponics systems, the farmers introduce a vessel known as a sump to enhance the bacteria’s multiplication.

The Importance of Regulated pH Levels

As you can probably imagine, bacteria, fish, and plants in an aquaponics system thrive under specific pH conditions. Most plants thrive in slightly acidic conditions, while most fish love slightly alkaline conditions. Creating the perfect balance calls for a compromise between the desired levels. For most aquaponics gardens, a pH range of 6.8-7.2 should be good enough for the bacteria, fish, and plants.

If your system is quite new and in the ‘cycling’ phase, it is advisable to keep the pH level at 7.0 or above. In this phase, the nitrifying bacteria are still setting up and might be slowed down by a lower pH. Keep in mind that pH levels vary naturally from time to time, so it’s always good to carry out periodic checks.

Aquaponics System Requirements

According to the FAO [1] (Food and Agriculture Organization), there are seven general requirements for an aquaponics system to run efficiently. Whether you are a beginner gardener, enthusiast, or seasoned aquaponics gardener, below are the main requirements to keep in mind.

Choosing Your Tank

A fish tank is a crucial component of any aquaponics unit. While any tank will probably work, it is recommended to use a rounded tank with a conical bottom. Such a shape makes it extremely easy to clean and gives the fish sufficient space to move around. If possible, go for fiberglass or inert plastic fish tanks due to their proven durability.

Water Circulation and Aeration is Important

Your aquaponics system can easily fail if the aeration and circulation are not right. Aeration makes sure that the water has sufficient dissolved oxygen for the fish. Additionally, optimum water circulation keeps the fish and bacteria healthy. When choosing water pumps, consider factors such as power usage to not end up with excessive power bills.

Water Quality is Essential

Quality water is the heartbeat of an aquaponics system. It is the only medium through which oxygen is transported to the fish, nutrients are transported to the plant roots, and fish waste is transported to the biofilter. Factors such as pH levels, oxygen levels, nitrogen levels, and temperature determine the overall water quality. For most systems, a temperature range of 18–30°C is ideal, a pH level between 6.8 and 7.2 and 5mg/liter of dissolved oxygen. You can get an all-in-one test kit to keep periodic tabs on these parameters.

Don’t Overcrowd Fish Tanks

The aquaculture section of your system is straightforward to manage when not overcrowded. The recommended stocking density is about 20 kilograms for every 1000 liters. Keep in mind that you can still go for a higher stocking density, but you will need to be more involved in the entire system’s day-to-day management.

Don’t Overfeed the Fish

As we mentioned earlier in the article, uneaten food is a source of ammonia harmful to fish. This food can rot inside the aquaponics system, adversely affecting the fish. It is worth noting that decaying food uses oxygen, resulting in oxygen deprivation for the fish. It is advisable to remove any waste food after a half-hour and reduce the next day’s portion.

Mix and Space Plants

It is advisable to plant leafy vegetables with short growth periods between those with longer growth periods. For example, plant green leafy vegetables between flowering plants such as peppers, cucumbers, and tomatoes. Doing this ensures sustained shaded conditions for the entire aquaponics system.

Balance the Plants and Fish

You can use a batch cropping system to ensure sustained fish and plant harvest. Additionally, make sure your supply of young plants and fish is consistent to avoid costly delays in your aquaponics system.

Types of Systems

There are four main types of modern aquaponics systems. Here is a brief look.

Deep Water Culture System

A deep-water culture system is also known as a raft-based system and uses a floating foam raft in a water channel. The floating raft serves as the planting container and has holes to allow the roots to float freely in the water. The water, on the other hand, is usually filtered to remove any solid fish waste. The raft-based system is ideal for fast-growing plants such as salad greens that do not have high nutrient requirements.

The deep-water culture system is also easily scalable, making it ideal for large-scale aquaponics systems. The floating raft can be made from different materials, but the most common is Styrofoam. With such a system, feel free to oxygenate the water manually for the fish’s benefit. Like most other systems, water has to be pumped from the aquaculture section of the system to the hydroponics section and back.

Media-Based Ebb & Flow System

As the name suggests, this system involves growing plants in growth media such as shale or clay pellets. The media serves two functions; mechanical filtration to remove solid waste and biological filtration to convert harmful ammonia to useful nitrates. Unlike raft systems, media-based systems are great for small-scale aquaponics gardens and are ideal for hobbyist gardeners. Large fruiting plants do particularly well in an ebb and flow system due to a supporting grow medium.

The growing medium is connected to a fish tank from which water is pumped. Once on the grow medium, the water is aerated and cleaned while plants absorb the nitrates. Typically, the plant tray sits above the fish tank to allow water to flow freely from the plant tray to the fish tank. You can choose from a wide range of growing media available online. Pea gravel is among the most common media.

Nutrient Film System

Nutrient film aquaponic systems work by feeding nutrient-rich water through a narrow space such as a PVC pipe. The pipes have holes drilled into them through which plants access the nutrients. The plant stems and leaves are above the pipe while the roots hang freely inside the PVC pipe. The nutrient film system is ideal for plants that require minimal support. These include a variety of herbs and strawberries. Additionally, the system is great for gardeners with limited space since the film system can be hung above other gardening areas.

Vertical Aquaponics

Vertical aquaponic systems involve stacking plants on top of each other. You can create one for yourself or buy vertical kits online. Nutrient-rich water gets into the system via the top tower and wicks down to lower troughs and back into the fish tank. This is arguably the most efficient system in terms of space usage. Like the nutrient film system, the vertical system works best for plants that do not require much support.

Benefits of Aquaponics

Compared to conventional gardening systems, there are numerous advantages to adopting aquaponics. Here is a look at some of the major benefits.

  • A single system has two major food products; fish and plants.
  • An aquaponics system barely requires pesticides or fertilizers, making the product significantly healthier and safer for human consumption.
  • An aquaponics system has very little waste, especially when compared to a conventional farming system.
  • An aquaponics system is extremely water-efficient. Compared to conventional agriculture, an aquaponics system only requires 1/6 of the water to produce several times more output per acre.
  • Aquaponics farming is extremely viable in conventionally non-arable areas such as sandy islands, deserts, and areas with extremely degraded soil.
  • Farmers have better control over production in an aquaponics system than they do in traditional farming.
  • Plants in an aquaponics system have their roots suspended in water. This leads to the development of smaller root structures, making it possible to fit more plants in an area than you would with a conventional gardening system.
  • The system can provide food for poor households, especially those without access to land.
  • The system does not require soil, thus eliminating the risk of soil-borne plant diseases.
  • The system has significantly better biosecurity as a result of reduced risk from external contaminants.
  • The system is entirely natural and mimics the world’s waterways, rivers, ponds, and lakes.
  • The system makes it easy to have sustained, intensive food production throughout the year.

Which fish Are Best for Aquaponics?

Fish are one of the three essential living components of an aquaponics system. However, there are numerous fish varieties out there that one can use in this system. How do you choose the best? It is important to consider aspects such as hardiness, water temperature requirements, growth rate, susceptibility to diseases, and feeding requirements. Here is a look at some of the commonly-used [2] fish varieties.


Tilapia is among the most common fish species among aquaponics gardeners. This fish reaches maturity quite fast, making it ideal for those keeping fish as a food source. Additionally, tilapias can tolerate huge variations in water temperature and pH. While this fish is omnivorous, it rarely preys on fingerlings or smaller fish. Before using tilapia in your aquaponics system, ensure that your state laws allow it. Some states discourage the use of tilapia to keep them off streams and lakes.


Catfish are among the most bred commercial freshwater fish. They are beloved for their extreme hardiness, adaptability to warm water conditions, and high resistance to parasites and diseases found in aquaponic systems. However, catfish tend to crown the bottom of tanks, making them unsuitable for people looking to have a high stocking density.


Trout is an excellent food source but considerably difficult to rear. For starters, the fish only thrive in cold water, which might, in turn, affect plant growth. Most plants might be affected by cold water, impeding the rate of growth. Additionally, plants such as squash, cucumbers, and tomatoes are unsuitable for the cold water suitable for trout.


Carp are adaptable and extremely hardy, making them ideal for most aquaponics systems. If you are a beginner gardener, this is arguably one of the best fish species to consider. Food-wise, carp are excellent for sandwiches and tacos. When bred in clean water, these fish do not have the characteristic muddy taste of other variants fished from lakes and rivers.

Goldfish and Other Varieties

Goldfish are ideal options for gardeners who are not looking to rear fish for food purposes. Goldfish are quite hardy and add some aesthetic appeal to your aquaponics system. You can also choose to go for the somewhat similar Koi fish. Other options to consider for an aquaponics system include guppies, bluegills, bass, and perch.


Aquaponics is arguably one of the most interesting fields in agriculture. The minimal space requirements and high food output make it worth considering for many people; beginners, enthusiasts, and seasoned green thumbs. By following the guidelines and tips outlined in this article, you can have an aquaponics garden up and running in no time.


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