20 SEPTEMBER 2015 • WORLD AQUACULTURE • WWW.WAS.ORG Aquaponics is an integrated fish and plant production technology. There are three distinct groups of people adopting this technology: new entrants, existing hydroponic operators and existing recirculating aquaculture system (RAS) operators. The potential for increased income is common to the interests and driving motivations of each group but other motivations, specific to the origin of the discipline involved, are also present. Existing hydroponic operators are primarily interested in accessing an organic nutrient solution for their plants, existing RAS operators are interested in a waste treatment outcome that avoids issues associated with waste releases and new entrants are mainly interested in a localized, niche-scale food production business. The RAS approach has a long association with aquaponics because most early aquaponic researchers had an aquaculture background. Aquaponics was seen historically as a technical approach to treat RAS waste nutrient streams so environmental impacts could be avoided or the associated cost of effluent disposal could be reduced, with the plants seen as a bonus outcome with some potential for sale. Although this long association is clearly present, some RAS practitioners have not fully adopted an approach to aquaponic design and management where emphasis is placed on the efficient and optimized production of plants. Plants require broad mixtures and concentrations of many nutrients to grow efficiently. Research with standard hydroponic plant culture practices has demonstrated that aquatic-based plant culture is complex and requires management with a high level of attention to detail that ensures optimized and efficient plant growth. For aquaponics to become economically successful, a good understanding of standard RAS-based fish culture is essential, but a good understanding of hydroponic plant culture is also required. If RAS scientists, engineers and operators are to adopt the aquaponic approach and provide knowledge, designs and expertise to develop an aquaponics industry, then they need to become more cognizant of plants and their requirements. This makes even more sense in the context of most aquaponic designs, which emphasize plant production, and that plants generate the majority of revenue in many situations. What is Aquaponics? The term aquaponics is an amalgamation of the terms aquaculture and hydroponics; with aquaculture generally referring to finfish culture and hydroponics referring to waterbased terrestrial plant culture. Aquaponics generally is defined as the combined culture of fish and plants in an aquatic environment or the integration of tank-based fish culture with hydroponic plant production or some variation on these themes. Therefore, at its root, aquaponics must include an aquatic animal and a plant in the production system. This definition of aquaponics principally concentrates on the two associated technologies of recirculating aquaculture systems and hydroponic plant culture and therefore, is suggestive of, and associated with, the technologies themselves and the related hardware or equipment involved. Aquaponics is not just about the technology or hardware involved but rather, like any integrated agriculture practice or method, is about the partitioning and sharing of nutrient resources between the fish and plants. Delving a little deeper into the aquaponic method, and exploring definitions most practitioners state and often laud, demonstrates that the aquaponic method commonly follows a similar conserved pathway. Fish are fed a complete feed, the fish incorporate some of the nutrients from the fish feed, the fish then produces solid and dissolved wastes, some wastes are converted by bacterial metabolic processes to nutrients available to plants and those nutrients are taken up and AQUAPONICS: a Nutrient Dynamic Process and the Relationship to Fish Feeds Wilson A. Lennard FIGURE 1. Phosphorus degradation over time in a no net nitrogen accumulation aquaponic environment (Lennard 2005). Aquaponics was seen historically as a technical approach to treat RAS waste nutrient streams, with the plants seen as a bonus outcome with some potential for sale. If RAS scientists, engineers and operators are to adopt the aquaponic approach and provide knowledge, designs and expertise to develop an aquaponics industry, then they need to become more cognizant of plants and their requirements.
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