WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 23 • The efficient and optimized use of water because plant nutrient availability is optimized. • The removal of any nutrient-rich waste streams, conferring no direct nutrient environmental impact. The mass balance approach to aquaponic system design has proven to be as productive as standard hydroponic methodology for plant production (Nichols and Lennard 2010, Lennard 2011; Figs. 1-3). The mass balance approach to aquaponic design, configuration and management allows the system to be designed and operated with exacting, predictable, optimized and efficient plant production outcomes in the context of using standard RAS design approaches and standard pelletized fish feeds. This also means that any plant species may be chosen and optimally integrated with any fish species to achieve production rates of both crops that equal stand-alone RAS and hydroponic equivalents. The approach includes the release and use of nutrients bound in solid fish wastes as well as dissolved fish wastes, so all available nutrients are utilized. Customized nutrient solution strength and mixtures result in the most efficient water use outcomes and any wastes streams are kept to an absolute minimum. This mirrors current standard hydroponic methods, where nutrient solutions are matched very precisely and specifically to the plant cultured. For example, the hydroponic nutrient solution mixture and strength for hydroponically cultured lettuce is very different from that used to culture tomatoes. The approach also allows the integration of standard, offthe-shelf, universally available RAS and hydroponic equipment. It can be easily adapted to any hydroponic method (raft, NFT, media, substrate systems using rockwool or coir) with no special widgets or devices required, thus keeping capital costs comparable to standard RAS and hydroponics. Finally, it provides a quantitative methodology for RAS designers and engineers that enables the nutrient and culture requirements of plants to be specifically met. Conclusions Aquaponics is becoming more prominent as an agricultural production technology and is currently so broadly applied that the term itself has no real practical definition. It is time a precise and practical definition is agreed upon and universally adopted so operators can legitimately claim the use of the term in a context where consumers can have the confidence that they are purchasing products that are grown in a way that actually means something and confers the implied advantages associated with the term. It is also time for the facts associated with the nutrient dynamics of aquaponic systems and the associated fish feeds utilized to become more apparent, understood and accepted so that scientifically verified methods are applied in a context that demystifies the technology. Finally it is time for modern methods of aquaponic design and configuration to be applied to the technology to allow the advancement of it to achieve true, predictable and productive, integrated agricultural production rates that match both standard RAS fish culture and standard hydroponic plant production. For this to happen in a context where current professionals can honestly and successfully meet the requirements of clients and operators, the industry must become more cognizant of the requirements of the plants and the nutrient dynamics associated with the integrated approach. References Lennard, W. 2005. Aquaponic integration of Murray cod (Maccullochella peelii peelii) aquaculture and lettuce (Lactuca sativa) hydroponics. RMIT University, Thesis for completion of Ph.D. RMIT University, Melbourne, Australia. Lennard, W. 2011. AVL aquaponics trial – progress report March 2011. Report produced for partial completion of a private, NZbased, commercial aquaponic trial. Published by Aquaponic Solutions, Melbourne, Australia. McMurtry, M., D. Sanders, P. Nelson and A.Nash. 1993. Mineral nutrient concentration and uptake by tomato irrigated with recirculating aquaculture water as influenced by quantity of fish waste products supplied. Journal of Plant Nutrition 16:407-419. Nichols, M. and W. Lennard. 2010. Aquaponics in New Zealand. Practical Hydroponics & Greenhouses Issue 115:46-51. Seawright, D., R. Stickney and R. Walker. 1998. Nutrient dynamics in integrated aquaculture-hydroponic systems. Aquaculture 160:215-237.
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