Climate change has impacted agricultural food production and the aquaculture industry in the state of Idaho (ID) through rising air temperatures, water scarcity, urbanization, and reduced snow-melting streamflow, threatening coldwater fish species, such as rainbow trout (Oncorhynchus mykiss). In response to these climate-driven challenges and variability, organic Controlled Environment Agriculture (CEA) emerges as a promising alternative that conserves water and protects crops indoors by mitigating environmental stressors. In this study, we developed a coldwater organic controlled-environment aquaponic system using system dynamics (SD) to grow rainbow trout (Oncorhynchus mykiss) with basil (Ocimum basilicum). We used the SD model to maintain the water level in the stock (including the fish tank and plant water reservoir), flow rate, environmental parameters (water temperature, pH, and electrical conductivity), as well as fish feeding, water quality, and nutrient dynamics (Ca²⁺, NH₄⁺, NO₂⁻, NO₃⁻, Cl⁻, Na⁺), and growth-related factors to optimize both fish and plant growth. We stocked 17 rainbow trout fry (average length 5.5 cm) according to the carrying capacity of our system to be raised for a year. We implemented the SD model in Stella Architect, where environmental and nutrient parameters were expressed as differential equations and numerically solved using Euler’s method with time-step approximation.
Results showed that the SD model effectively predicted total ammonia nitrogen, nitrite (NO₂⁻), nitrate (NO₃⁻), and other nutrient and water quality parameters, closely matching observed values (R² > 0.90) and demonstrating strong accuracy. The model also maintained nutrient delivery in coldwater, ensuring stable conditions for fish and plant growth. This was reflected in trout performance, with a feed conversion ratio of 1.16 and a specific growth rate of 1.2% per day over 90 days, indicating efficient feed utilization in the coupled recirculating system. Basil grew vigorously without additional fertilizers, achieving a yield of 11.9 kg/m², with an average plant height of 32 cm and a leaf area of 41.2 cm² at harvest. These findings highlight that organic controlled-environment aquaponics can simultaneously support coldwater trout and high-yield basil production as a resilient approach to sustainable food production in climate-vulnerable regions across Idaho and beyond.