High capital investment is one of disadvantages of current recirculating aquaculture systems (RAS) that restricted adoption and application of them. Biofilters are very important and expensive components of RAS, as proper selection of them are critical to both the technical and economical success of a RAS. Hence In this research application and activation of four types of biofilter media (barley straw, wood chips, sponge and PVC pore pipes) in the common carp recirculating aquaculture system were studied. 12 pilot recirculating aquaculture systems constructed to conduct this research. Each system consisted from a polyethylene tank (90 L) for rearing of fingerlings and a black polyethylene tank (45 L) as a biofilter reactor. Stocking density of common carp fingerlings (mean weight: 4.8 g) in the each tank was 50 individuals. Results showed that TAN and NO2-N concentrations increased initially and then decreased during activation period. Nitrate nitrogen increased during the activation period of biofilters. All biofilters reached steady state conditions and activated completely at days 28-31, while PVC biofilter had relatively high concentration of NO₂-N even at day 31. Growth and feeding parameters showed no significant differences between treatments, but there was significant difference between flow throw system and treatment PVC (p<0.05). In conclusion barley straw, wood chip and sponge biofilters were well activated under common carp recirculating aquaculture systems.