The economic and environmental sustainability of aquaculture depends significantly on the nature and quality of the fish feed used. One of the main criticisms of aquaculture is the need to use significant amounts of fish meal, and other marine protein sources, in such feed. Unfortunately, the availability of the oceanic resources, typically used to produce fish feed, cannot be utilized indefinitely to cover the worldwide feed demand caused by ever-increasing aquaculture production. In light of these considerations, this study estimates how aquaculture farm economic outcomes can change by introducing insect meal into the diet of cultivated fish. Several possible economic effects are simulated, based on various scenarios, with different percentages of insect flour in the feed and varying meal prices using a case study of a specialized off-shore sea bass farm in Italy. The findings indicate that the introduction of insect meal—composed of Tenebrio molitor—would increase feeding costs due to the high market prices of this flour and its less convenient feed conversion ratio than that of fish meal. Therefore, the expected environmental benefits of using this highly promising insect meal in fish feed do not align with the current economic interests of the aquaculture industry. To our knowledge, this is the first study to investigate this theme, and it must be noted that our findings cannot be generalized widely because a specific case study was used. Nevertheless, our findings suggest that efforts should be made—at least at the farm level—to find profitable ways to encourage the introduction of this attractive alternative to guarantee both economic and environmental sustainability in the near future.