Aquaponics is an integrated multi-trophic production system (polyculture) consisting of two technology applications combination between aquaculture (fish farming) and hydroponic (soil-less) cultivation of vegetables or plants. It is also known that aquaponics is a method that has a role in the larger context of sustainable intensive agriculture, particularly in small-scale applications. It can grow significant volumes of food in areas and conditions where soil-based agriculture is difficult or impossible, and it offers supportive and collaborative ways of vegetable and fish production (Somerville et al., 2014). Aquaponics in environmental aspects helps by avoiding the escape and pollution of water from aquaculture wastewater and provides more management of water and productivity. Aquaponics do not use fertilizer chemicals, pesticides, or weeds to prevent any residues.
Figure 1. Aquaponic Nitrogen Cycle
In aquaponics, the biological process involved is nitrification, an important part of the nitrogen cycle found in nature. The idea is that when the fish excrete nutrient-rich waste, it can fertilize the plants and filter the water for the fish. The process starts with the Nitrosomonas bacteria break down the fish waste which is largely made of ammonia (NH3) into nitrite (NO2) and then the second type of bacteria, Nitrobacter bacteria convert the nitrite (NO2) into nitrate (NO3) that become the dissolved nutrients, which plants need to thrive in the hydroponic component (Figure 1). The principle of this system enables fish, plants, and bacteria symbiotically to live and cooperate, providing the appropriate balance for the system, and producing a healthy growth environment (Ujjania et al., 2021).
Figure 2. Main components of an aquaponic.
There are several basic components required for an aquaponics system. This system uses Recirculating aquaculture systems (RAS) which are self-contained growing environments for producing aquatic organisms (Pattillo, 2017). The ‘hardware’ of an aquaponic system consists of fish tanks, water, and air pumps, the solids removal units such as drum filters or settlers, biofilter, plant grow beds and the plumbing materials for water supply (Figure 2). For water management, there are two types of water management which are closed-loop (coupled system) and open-loop (decoupled system). Closed-loop (coupled systems) is a system where water is continuously circulated from the RAS to the hydroponic unit, and back to the RAS. While open-loop (decoupled system) or also known called as decoupled aquaponic systems (DAPS), the water is separately recirculated within each system and is supplied on-demand from the RAS to the hydroponic unit, but it does not flow back to the system which the two systems between RAS and hydroponic unit are connected by a one-way valve (Sallenave et al., 2019).
There are several types of hydroponic systems used in aquaponics. One of them is the Nutrient Film Technique (NFT), in which the plant roots in this arrangement are suspended in channels called valleys through which a thin layer of nutritional solution flows, keeping the roots wet but not logged (Mohammed et al., 2016). Next, the Media bed technique, the most popular design for small-scale aquaponics which the medium serves as a mechanical and biological filter as well as a support for the plants' roots (Dunn, 2016). Besides that, there is also the Deep-Water Culture (DWC) known as the raft method or floating system, the nutrient-rich water is circulated through long canals at a depth of about 20 cm while rafts (usually polystyrene) float on top (FAO, 2015).
In an aquaponics system, there are also advantages and disadvantages. The advantages of the system are the preservation of water resources, lessened operating costs compared to aquaculture or hydroponics separately, high level of biosecurity aimed at minimizing the risk of transmission of infectious disease and fewer contaminants, recycling of non-renewable resources such as phosphorus, potassium, and of renewable, but scarce ones such as water, able to operate in a wide range of climates and both rural and urban settings, allowing for the production of family food or income crops and also an efficient use of nutrient source (fish feed). For the disadvantaged part, the start-up is more expensive compared to other technologies, a thorough understanding of the species (fish, plants, microbes) involved is required, without heavy investment in greenhouse technology, requirements for fish and plants may be varied and cannot be fulfilled at each site, management daily is required and requires electricity, supply of seedlings and fingerlings (young fish).
In a nutshell, aquaponics is a unique, fast-growing, environmentally friendly agriculture technique that combines RAS and hydroponics systems and also offers all-year-round productions. Overseason leafy greens, herbs, and vegetables may be a key source of revenue for aquaponic farmers as they can benefit from much higher pricing. This system can produce high-quality vegetables, plants, and aquatic species. Aquaponics can be done on a small scale or a large one, ranging from a hobbyist's bench-top aquarium to a multi-acre commercial operation able to produce large quantities of fish and plants every year. It also shows the efficient technology by providing the symbiotic environment by producing plant base and fish and increasing sustainability.
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2. FAO, Fisheries and Aquaculture Departments in FAO (2015). Deep Water Culture Aquaponic Unit: Step by Step Description. Retrieved from http://www.fao.org/3/CA2549EN/ca2549en.pdf
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Sallenave, R., & Shultz, R. C. (2019). Decoupled aquaponics: A comparison to single-loop aquaponics.
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