Aquaponic trends and challenges – A review

Abstract This article reviews current literature published on aquaponics, a growing technology which uses aquaculture effluent to grow plants. Aquaponics offers a solution to several sustainability issues, such as, limited water availability, environmental pollution, increasing fertilizer cost, and depletion of fertile soils. The commercial and scientific application of aquaponics is growing; however, there is yet to be a review which holistically analyses scientific literature to indicate what type of system performs optimally, what will be the most dominant horticultural challenges as the commercial sector expands, and what direction of aquaponic research will be most impacting. This review analyzed over 529 publications on aquaponics, from 1978 to 2018. Through a systematic process, 257 of the most constructive publications were further analyzed and organized into varying groups based on content. The review found that in the past three 3 years, over 160 scientific articles have been published on aquaponic technology, detailing numerous trends, technological advancements and challenges associated with the system, consolidating the expansion of aquaponics and the need for a review. From publications investigating trends, it was found that decoupled aquaponic systems are becoming increasingly popular over coupled aquaponic systems, a deep water culture hydroponic component and media bed component are optimal for commercial and research applications, respectively; Tilapia and dark leafy vegetables are the most successful species used and Nitrospira may play a more important role in the aquaponic nitrification process than expected. From publications investigating challenges, it was found that commercial aquaponics will face difficulty growing high value flowering crops such as sweet peppers, tomatoes or cucumber, as a result of suboptimal nutrient ratios in aquaponic solution, specifically the reduced K + , Mg + , and Ca + . Holistically, it was found that the most important aspect of aquaponics that needs future research is the role plant promoting microbes play in nutrient uptake. Considering plant growth promoting microbes are likely the cause of aquaponic plants being able to achieve yields similar to that of hydroponics, despite nutrient levels being significantly lower, future research in this field can be paramount to the beneficial use of microbes in all plant production systems.