Against the background of the stagnating EU aquaculture sector growth in contrast to the increasing sector size at world level (including Norway) , it is important to address prevailing hindering factors such as import pressure or social pressure due to actual and perceived environmental impacts. Within the H2020 project Green Aquaculture Intensification (GAIN) innovative production tools based on the principles of circular economy were developed and evaluated in order to facilitate the paradigm shift of eco-intensification in European aquaculture. While the valorisation of side-stream products is beneficial for a more sustainable production, related changes in production practices, may impact capital investment, labour input or energy demand, all of which affect costs. We applied an established benchmarking approach to contrast today’s economic performance of “typical farms” using the conventional ensilage method with their profitability when processing mortalities within a drying unit. Further, in-depth cost-benefit analyses were conducted for a theoretical decoupled algae aquaponics system ( Ulva lactuca) utilizing disposal water from smolt RAS production; as well as an input-output based economic analysis for the valorisation of aquaculture fish by-products (FBP) on industry scale. The results reveal a promising economic balance for various market opportunities such as selling dried mortalities to the pet food sector or Ulva lactuca to the Asian market with the side-effect of reducing the nutrient load of European smolt waste water and potentially increasing smolt production. Processing various FBP into secondary products also proved to be promising approaches for fish protein hydrolysate, peptones and their further use as medium e.g. for lactic acid bacteria . The profitability of the examined pathways were based on accessible market prices. F urther key aspects for future marketing success will also include market access and consumer demand.