This thesis investigates the replacement of fishmeal with black soldier fly (BSF) meal in the diets of common carp (Cyprinus carpio), evaluating its effects on growth performance and economic viability across replacement levels of 0%, 25%, 50%, and 75%. The study, conducted over 8 weeks at the University of Debrecen, found that 75% BSF meal substitution significantly enhanced growth parameters, such as final body weight (318.9 g) and weight gain (222.57 g), compared to the control (249.13 g and 152.8 g, respectively). Feed conversion ratio showed a non-significant improvement from 1.68 to 1.36, while survival rates remained high (97–100%), indicating BSF meal’s nutritional safety. However, feed costs increased from €1.11/kg in the control to €1.80/kg at 75% replacement, reducing economic profitability due to the high cost of BSF meal (€3.75/kg versus €1.85/kg for fishmeal). The research concludes that BSF meal is a nutritionally effective alternative to fishmeal but is currently limited by economic challenges stemming from high production costs and EU regulatory constraints. It recommends reducing BSF meal costs through regulatory adjustments to enhance its feasibility as a sustainable aquafeed option.