Aquaponics is becoming popular in many countries including the Sultanate of Oman where there is lack of freshwater supply. However, there is a need to determine the plant and fish species that can be grown and the financial feasibility of aquaponics considering the environmental conditions in Oman. The main objective of the research was to assess the technical and financial feasibility of growing high-value species in an aquaponic system in a greenhouse. The two specific objectives are: 1) To determine the most suitable plant species in combination with koi carp or tilapia within an aquaponic system in a greenhouse and 2) To analyze the costs and benefits of such aquaponic system in a greenhouse setting.
Two experiments were designed. The first experiment tested growing tilapia with high-value plants (spinach, cabbage and lettuce) in floating versus media-based growing system, for 3 months. The second experiment compared the growth of tilapia versus koi carp in combination with strawberry and mint in floating versus media-based aquaponic system., 4 four months. The fish were fed with 2mm sinking pellets at around 5% of their average body weight per day and given in 2-3 rations per day. The weight and length of the fish were measured every month. Growth of plants in terms of height and number of fruits in the case of strawberry and number of stems in the case of mint was determined every month and the total numbers of surviving plants were also counted. Statistical tools such as ANOVA, t-test and Tukey’s test were used to analyze variables, such as weight, length and mortalities of species.
In the first experiment final weights of spinach and tilapia were slightly higher in the media-based than in the floating system but their differences were not significant. In the second experiment, both tilapia and koi in the media-based system had higher average growth and survival; however, there was no significant difference between the two systems. The media-based system also showed higher average growth in terms of the number and weight of fruits (strawberry) and also in the average number of stems (mint), however, there was no statistical difference between the two systems. The financial feasibility study was conducted using cost-benefit analysis. Based on the data from the experiments, the total revenue calculation considering the market value of each of the plant and fish species, investment and operating costs, it can be concluded that it is feasible and profitable to use either floating or media-based system for growing the tested plants especially lettuce and mint along with koi carp in a greenhouse setting. Investment costs can be recovered in two years. If implemented commercially, aquaponics can help address issues such as water management, food security and sustainable production of fish and vegetables to meet the increasing demand.