By definition, aquaponics is the symbiotic cultivation of plants and aquatic animals in a recirculating environment. What it could offers to the world of aquaculture and agriculture is hugely promising, yet its name is rarely uttered within the food sector.
Advocates of aquaponics will say that a well balanced system could eradicate the costs of feed, supplements, continuous employment and waste management. In return, providing a variety of high quality, natural food products in high yielding quantities, but the reality of the technology in practise today adheres to few of these promises.
Modern aquaponic systems usually take place within greenhouses in order to maximise conditions. Water from the fish tank is filtered and recirculated by the biological methods of the plant. Ammonia, nitrates, nitrites, and phosphorus are stripped away and then the freshly cleansed water is recirculated back into the fish tanks. In return, nutrients generated from fish manure, algae, and decomposing fish feed - that would be toxic to the fish - serve as liquid fertilizer to hydroponically grown plants.
Essentially what these systems create is a self sustaining renewable system that does not require fertilisers for the plants, or fresh water for the aquatic animals. Current systems still require the addition of fresh salt and water replacement for evaporation and plant uptake, but in principle even these inputs could be eliminated.
Practical Uses
The use of aquaponics is not a new idea. Some people point back to ancient Egypt when tracing its roots, but a modern view of aquaculture stems from the permaculture movement that began as an agro-ecological design theory in the 1970's.
Developed by Australians Bill Mollison and David Holmgren, the idea was used to create stable agricultural systems. This was a result of their perception of a rapidly growing use of destructive industrial-agricultural methods. Since then, aquaponics has become a movement in its own right, serving as a model of sustainable food production for both land-based and aquatic organisms.
A recent publication by the National Sustainable Agriculture Information Service (ATTRA) took a look at present day aquaponic systems in the US and current research into the production methods. According to the publication, Aquaponics - Integration of Hydroponics with Aquaculture, farmers are beginning to take an increasing interest in aquaponics due to the low input and waste management costs and also the green credentials that they provide.
For all its potential aquaponics must currently utilise complex technology and the skilled ability of workers to simultaneously monitor, manage and market the different types of agricultural products it creates. However, recent innovations have transformed aquaponic technology into a viable system of food production, claims the report. These systems can be highly successful, but they still require special considerations. Knowledge of both hydroponics and aquaculture are currently essential to the management of an efficient system.
Not all plants are adapted to strive in aquaponic greenhouses. Similarly, nor are all aquatic creatures suited to aquaculture systems. Furthermore, those plants and fish often require specific conditions to strive. pH, temperature, oxygen levels, feed are just some of the aspects that must be managed for optimum growth. It is the bringing together of these right conditions that makes aquaponics so difficult.
On top of that, managers must also harmonise the stocking densities of the chosen plants and animals. "Matching the volume of fish tank water to volume of hydroponic media is known as component ratio", explain the report. "Early aquaponics systems were based on a ratio of 1:1, but 1:2 is now common and tank: bed ratios as high as 1:4 are employed. The variation in range depends on type of hydroponic system (gravel vs. raft), fish species, fish density, feeding rate and plant species,"
However, if the basic set up of the system is correct, yields can more than compensate for the hard work. Not only will the input cost be minimised, but also the value of the product will be high. Products should be well managed and healthy, containing no artificial chemicals, or hormones and having no adverse effect upon the environment.
The products can then be marketed as organic and in return demand a greater price at market. Unfortunately, although organic aquaculture has a valued market in many countries, there has been no global consensus on its definition and a US Department of Agriculture accredited organic label has remained entirely allusive. For this reason, a movement towards organic aquaculture has been severely hampered.
Not So Radical Thinking
In many ways, the complexity of aquaponics requires an understanding of all life. Farmers must engineer a whole ecosystem that caters for the need of all the plants and animals that live within it. And yet, essentially, aquaponics lets nature do what it does best by allowing it to deal with the complex underworld of interactions, soil structures and micro-organisms that we really do not understand. Rather than attempt to bend nature to the whim of human knowledge, it realigns our knowledge on its path.
Aquaponics should not be judged and seen merely through the green-tinted lenses of eco-friendly eyes, it should be mutually acknowledged for the advantages it can provide on economic, health and market grounds. Not only does it harmonise yield products, but it also fuses natural processes with highly advanced technological ones to derive the best of both.
Unfortunately, with the rapid advancement of huge machines and intensive monoculture operations behind us, it can be difficult to look again and see a natural agricultural process take its place and be just as efficient. But time and again, the problems that intensive operations encounter have proved difficult to overcome with manmade contraptions. Nature already has the answers to most of our problems, it is merely learning to see and listen to them that often hinders our advancement.
Example of Current Projects from ATTRA
The North Carolina State University System
In the 1980’s Mark McMurtry (former graduate student) and the late Doug Sanders (professor) at North Carolina State University developed an aqua-vegeculture system based on tilapia fish tanks sunk below the greenhouse floor. Effluent from the fish tanks was trickle-irrigated onto sand-cultured hydroponic vegetable beds located at ground level. The nutrients in the irrigation water fed tomato and cucumber crops, and the sand beds and plant roots functioned as a biofilter. After draining from the beds, the water recirculated back into the fish tanks. The only fertility input to the system was fish feed (32 percent protein).
The North Carolina State University System
In the 1980’s Mark McMurtry (former graduate student) and the late Doug Sanders (professor) at North Carolina State University developed an aqua-vegeculture system based on tilapia fish tanks sunk below the greenhouse floor. Effluent from the fish tanks was trickle-irrigated onto sand-cultured hydroponic vegetable beds located at ground level. The nutrients in the irrigation water fed tomato and cucumber crops, and the sand beds and plant roots functioned as a biofilter. After draining from the beds, the water recirculated back into the fish tanks. The only fertility input to the system was fish feed (32 percent protein).
The University of the Virgin Islands System
James Rakocy, PhD, and associates at the University of the Virgin Islands (UVI) developed a commercial-scale aquaponic system that has run continuously for more than five years. Nile and red tilapia are raised in fish The University of the Virgin Islands System James Rakocy, PhD, and associates at the University of the Virgin Islands (UVI) developed a commercial-scale aquaponic system that has run continuously for more than five years. Nile and red tilapia are raised in fish
The Freshwater Institute System
The Freshwater Institute in Shepherdstown, West Virginia—a program of The Conservation Fund, an environmental non-profit organization—specializes in aquaculture research and education. For years, the institute has specialized in cold-water recirculating aquaculture systems raising trout and arctic char. The institute helps Appalachian farmers set up two types of aquaculture systems: (a) an indoor, hightech recirculating tank method and (b) an outdoor, low-tech recirculating tank method.
The Cabbage Hill Farm System
Cabbage Hill Farm is a non-profit organization located about 30 miles north of New York City. The foundation is dedicated to the preservation of rare breeds of farm animals, sustainable agriculture and loca l food systems, and aquaponic greenhouse production. Tilapia fish and leaf lettuce are the main products of the Cabbage Hill Farm system, though basil and watercress are also grown in smaller quantities. In addition to hydroponics, water passes through a constructed reed bed outside the greenhouse for additional nutrient removal.
The New Alchemy Institute
The New Alchemy Institute in East Falmouth, Massachusetts, conducted research on integrated aquaculture systems during the 1970s and 1980s. Although the institute closed in 1991, New Alchemy publications on greenhouse production and aquaponics provide historical insight to the emerging bioshelter (ecosystem greenhouses) concept and are still a valuable resource for technical information.
January 2009
