Due to limited water resources, the use of intensive aquaculture systems is essential. This study compared the performance of a biofloc system and a semi-recirculating system in terms of physiological responses, immunity, and growth indices of common carp (Cyprinus carpio) under commercial farm conditions. The experiment was conducted over 16 weeks in rectangular concrete ponds with cross-current flow (MCR system). Juveniles with an average initial weight of 100.4 ±0.08 g were stocked into two treatments. In the semi-recirculating system, 50% of the water volume was exchanged daily, and fish were fed a diet containing 30% crude protein. In the biofloc system, no water exchange was performed, the carbon-to-nitrogen ratio was maintained between 12:1 and 15:1 by adding molasses, and a diet with 25% crude protein was used. The results showed that the concentrations of total ammonia nitrogen, nitrite, nitrate, TDS, and TSS were significantly higher in the biofloc system than in the semi-recirculating system (P < 0.05); however, these values remained within the tolerable range for the fish. Final weight, weight gain, specific growth rate, and feed conversion ratio showed no significant differences between the two systems (P > 0.05). While daily protein intake was higher in the semi-recirculating system, the protein efficiency ratio was significantly improved in the biofloc treatment (P < 0.05). Proximate carcass composition showed no significant differences between treatments (P > 0.05). The glucose, urea, and creatinine levels were significantly higher in the biofloc system (P < 0.05), indicating a mild physiological stress response. In contrast, serum lysozyme activity was significantly elevated in the biofloc system (P < 0.05). Overall, despite the reduced dietary protein level and zero water exchange, biofloc technology achieved growth performance comparable to that of the semi-recirculating system while enhancing the immune responses of common carp.