Agriculture, which is defined in simple terms as the science of farming, has proven to be a major source of food, wool, and other products to humanity.
Growing of crops via soil cultivation and the rearing of animals – including fishes, are two major types of agriculture.
During soil cultivation, manure (excretions from animals) can be used to make the soil more fertile so as to increase output. However, accumulation of manure in water can lead to increased levels of toxicity which can in turn damage crops and other animals. This has led to the creation of more advanced methods of farming, one of which is Aquaponics.
In this article, we'll cover:
- A clear explanation of exactly what aquaponics is
- A brief history of aquaponics and its origins
- A detailed explanation of the science and mechanics involved in an aquaponic system as well as the different types of systems that exist
- The components that make up an aquaponic system and the basics of operating it
- The benefits and reasons for why aquaponics is a revolutionary system of gardening that everyone should learn about
So, what is Aquaponics?
Aquaponics is a system of agriculture that incorporates two different types of agriculture – aquaculture and hydroponics, hence the name ‘Aquaponics’ which is a combination of the words ‘Aqua-culture’ and ‘Hydro-ponics’.
Aqua-culture deals with farming of aquatic animals such as fish, prawns, crayfish, and snails using tanks, while hydroponics involves the cultivation of plants in water.
Aquaponics combines these two types of agriculture in a symbiotic environment where both the plants and animals benefit from one another in order to thrive and grow.
A Brief History
Aquaponics is a relatively new branch of modern agriculture as the term itself only came into being in the 1970s. Aquaculture and hydroponics are systems of agriculture that only started gaining grounds about half a century ago. However, the earliest example of one of the two branches of aquaponics (hydroponics) dates back to around 1000AD when the Aztec Indians cultivated plants on rafts on the surfaces of lakes. Aquaculture, on the other hand, was formerly carried out in vast ponds, which consumed large quantities of water and land (Palouse-Clearwater).
In an effort to redress the issue, aqua-culturalists had to create the Recirculating Aquaculture System (RAS). Experiments carried on in the early stages of the RAS sought to ascertain the effectiveness of aquatic plants at consuming and filtering nutrients found in wastewater that comes from aquaculture farms. With positive results proving the effectiveness of aquatic plants at purifying water, aquaculture and hydroponics were then combined as an integrated agricultural system.
How Aquaculture and Hydroponics Work Together
Aquaponics, as has been mentioned earlier, is a combination of aqua-culture and hydroponics. Hydroponics, as an agricultural system on its own, does not only require that plants be fed using a good amount of costly nutrients but also that the hydroponic system be flushed regularly. This regular flushing is usually accompanied by the issue of waste disposal. Aqua-culture, on the other hand, requires that excess nutrients be constantly removed from the system which means replacing this nutrient-rich water with fresh water on a daily basis.
An aquaponic system takes these two individual defects and combines them to thrive. Here, the aqua-culture system feeds the hydroponic system with nutrient-rich water and during this process, nitrifying bacteria in the hydroponic system breaks down the nutrients in the water first into nitrates which are subsequently used by nutrients as plants. The water, now free of nutrients is then recirculated back to the aqua-culture system.
The Aquaponic Cycle
In the aquaponic cycle, the plants are planted on the grow bed and the fish are placed in the fish tank. Of course, the size of both the grow bed and the fish tank will depend on the purpose of the aquaponic system – whether it is for individual or commercial purposes. There are five main inputs to the aquaponic system. These are water, light, feed given to fish and other aquatic animals, electricity to pump and filter water, and of course, oxygen.
Once the fishes are placed in the tank, the cycle begins. Feed is given to fish and other aquatic animals to make them grow healthily. After eating, the fish pass out waste. Their excrement contains ammonia which cannot be absorbed by plants. In addition, excess ammonia in the fish tank might prove hazardous for fishes and other aquatic animals.
This ammonia-concentrated water is then fed to the grow bed just beneath the plants. When the water gets to the grow bed, bacteria found in the soil break down the ammonia found in the fish excrement into nitrites, and then further broken down into nitrates. These nitrates are then absorbed by plants together with vermicompost – a converted version of solid fish waste to grow healthily (Pattillo, 2017).
With the conversion and absorption of the ammonia and nutrients from the water, the water now becomes clean and fresh enough for fish to thrive in.
Electricity is used to pump the water to and from the fish tank and is also used to filter the water when it leaves the grow bed. Before the water from the grow bed is sent back to the fish tank, it is oxygenated to provide fish with oxygen.
With the water fresh, filtered and oxygenated, it is then recirculated to the fish tank where the cycle begins again.
It is important for the area where the aquaponic system is found to be exposed to sunlight or sufficiently lit since plants need light to grow.
Components of an Aquaponic System
Aquaponic systems can be built both indoors and outdoors and may vary in size depending on the individual. What is important, however, is what is needed to build one. So, here are the basic components of an Aquaponics system:
This is a rectangular or square box used in raising plants in an aquaponic system. They are usually made of black recycled plastic. The plastic material used in making this box coupled with its black color play the vital role of absorbing heat, which warms the soil while also retaining moisture to help plants grow.
This is where fish will be kept. The size of the tank will ultimately depend on and define the flexibility and size of the aquaponic system. It is therefore important to consider this early enough. If you are growing fish for table purposes, it is important to use a large tank that is capable of holding at least 50 gallons of water and is at least 18 inches. The material for the tank really does not matter insofar as it is lined with an EPDM Pond Liner.
Fish play a very important role in the aquaponic system, not just because they are among the aquatic animals being cultivated but because their excrement also acts as a source of natural fertilizer for the plants being cultivated. The types of fish that can be cultivated using aquaponics will be discussed later.
Just as fish are not only important for the obvious reason, plants too play an important role in the aquaponic system apart from their obvious role. Waste from fishes in the aquaponic system acts as food for plants which suck up all the rich nutrients in the water from the fish tank. By so doing, the water fed back to the fishes is clean and fresh water which is the type of water ideal for growing fish.
This plays a very vital role in the aquaponic system. Water from the fish tank fed to the grow bed contains a lot of ammonia from fish waste. This ammonia, if not broken down can end up being harmful to the plants. Bacteria (nitrifying bacteria to be precise) converts the ammonia found in fish waste into nitrites, and eventually into nitrates. These nitrates are the only form of nitrogen which plants use to grow. In addition, they also convert solid fish waste into vermicompost which is used up by plants as food.
Operation and Maintenance
Building an aquaponics system is one thing, operating maintaining it is entirely something else. Just like with any other agricultural system, proper operation and maintenance are necessary to yield bountifully. It is therefore important to make sure your aquaponic system is always in great shape. And here’s how to effectively operate and maintain your aquaponic system.
- First, it is important to verify the quality of the water you are using. It is important to use chlorinated water when filling up your system. Anything less can bring about undesirable outcomes. If you are unable to use chlorinated water, then, it is important to chlorinate the water by putting a quart of Clorox in every 600 gallons of water. Once that has been done, you are ready to start your pump and run your system. Be sure to check the system at least, once every four days and repeat the process if necessary.
- The next thing to take into consideration is that your fish will need fertilizer so, always try to have some fish feed around. Consider buying little fish and raising them in the system than going for bigger fish to reduce cost and try to feed your fish daily.
- Check your fish tank’s temperature daily as it is important to create the ideal environment for the specific aquatic species you have. It is therefore also important to know the ideal temperature for the fish you are raising.
- Also, check your system for insects on a weekly basis as it is safer to tackle insect problems early enough before they become uncontrollable.
- Also, check your system’s pH levels on a weekly basis as it has a direct effect on the ability of your bacteria to reproduce, the ability of your plants to absorb nutrients and the overall health of your fish. Aim for a pH level of between 6.8 and 7.0 and add potash or lime should it fall below 6.5.
- Check the system’s nitrate levels at least once a month. A spike in nitrate levels might mean that there aren’t enough plants to absorb the nitrogen that is being converted by the nitrifying bacteria. You can solve this problem by adding more plants, adding a new grow bed to your system or reducing the number of fish you have.
- Check all pumps and plumbing daily and clean them at least once a month to allow for effective circulation. To reduce the stress and hassle that accompanies cleaning, run a hose of high-pressure water through each and every component of your system.
Types of Aquaponics Systems
There exist four main types of aquaponic systems. These are discussed below:
Raft Based/ Deep Water Culture (DWC)
With this system, plants are grown aboard rafts (usually polystyrene boards) floating on water. Usually, the raft carrying plants is placed in a tank different from the tank carrying fish. Water from the fish tank is fed via filtration components to the tank containing the rafts and then recirculated back to the fish tank. Nitrifying bacteria are found in the raft tank and remain there throughout the system.
One major benefit of the raft system is that it greatly reduces potential water issues and stress since the extra amount of water in the raft tank buffers the fish tank when need arises. Also, in a large aquaponic system, rafts can make planting and harvesting easy as seeds can be planted on one end of the raft tank (which usually spans areas of square meters).
During growth, the rafts make their way to the other side of the tank where the mature plants are harvested. The harvested raft can then be replanted and the process starts all over.
This method is beneficial because it used fewer components than a traditional aquaponic system. Here, the grow bed is filled with perlite, gravel or some other media. From time to time, the bed is fed with water from the fish tank. The water eventually drains back to the fish tank after all waste including solids has been broken down within the grow bed.
In some cases, worms can be added to the grow bed to enhance waste break-down. However, despite the fact that this method is easy to operate, it produces far less than other systems and thereby used for hobby purposes.
Nutrient Film Technique (NFT)
Here, plants are grown in long narrow channels with a constant flow of shallow water from the fish tank down each channel enough to provide the roots of the plants with nutrients, water and oxygen.
The water flows through the channel where the plants are found and past the filtration components back to the fish tank. However, because the volume of water is not enough for bacteria to survive, a different biofilter is needed. Also, because of the organic nature of this technique, hydroponic NFT systems are generally not big enough for use in aquaponics. Despite the potential it shows, it is the least used aquaponic system.
This type of system can be built in all sizes and is ideal for urban settings where space is limited. Here, tall containers are used to grow plants. The fish tank is placed at the bottom of the system and then tall containers are placed vertically with a system designed to circulate water throughout the system.
A major advantage of this system is that it allows for a single fish tank to grow more plants. Gravity also plays a very important role in this system as water will need to leave the fish tank below all the way up to the plants before returning to the tank. It is therefore important to build a structure that works perfectly and is convenient for maintenance.
Types of Fish and Plants:
Almost any type of freshwater fish can be used in an aquaponic system. However, some recommended edible fish types include tilapia, trout, carp, catfish, largemouth bass, sunfish, crappie, and barramundi among others. Other fancier non-edible fish types recommended for aquaponics include koi and goldfish.
For plants, aquaponic systems are ideal for leafy plants such as lettuce, mint, chives, basil, kale and other common houseplants. Plants with higher nutritional demands such as peppers, beans, peas, cauliflower, tomatoes, broccoli, cucumber and cabbage require well-established and heavily stocked systems. Other crops that can be grown in aquaponic systems include carrots, beets, radishes, lemons, limes, onions, sweet corn, and other edible flowers (Nelson and Pade).
Benefits to Aquaponics
- Aquaponics uses about 90% less water than soil-based gardening since the water in the system is recirculated. As a result, only water that evaporates or water absorbed by plants is replaced. This, in turn, makes water available for other uses and reduces the amount of water wasted on cultivating crops (Common Sense Home, 2017).
- Aquaponics is an inexpensive means of agriculture. Apart from major equipment and components like tanks, filtration systems, grow beds, plants and fish, which can be used for a long time before changing, it basically makes use of just one other input in order to produce two crops (fish and plant). Electricity costs are also greatly reduced as it requires only energy to run pumps and oxygenate fish.
- Aquaponics produces far more organic plants than soil-based cultivation. This is because it doesn’t make use of pesticides and chemical fertilizers as these can be hazardous to fish and other aquatic species.
- With aquaponics, more can be produced on a single square foot than with soil-based cultivation. This is because plants grow 2-3 faster than they do on soil. Also, plants can be packed twice as densely as they can on soil.
- It is easy to set up and can be set up indoors and outdoors. It can also be used anywhere as it does not depend on the fertility of the soil. As such, it can be set up in places such as schools, restaurants, garages and home basements.
- Finally, it gives you the satisfaction of growing and eating your own fish and vegetables!
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