A single-stage aerobic membrane bioreactor (MBR) has been developed as an efficient and compact system for aquaculture wastewater treatment. In this study, the role of sponge media in an MBR treating synthetic aquaculture wastewater was investigated. The MBR was operated at a hydraulic retention time of 4 h and its treatment performance during the operation with and without sponge media was compared. During 120 days of operation, there was no significant effect of sponge media on the organic, ammonium or organic nitrogen removal observed in the MBR. High organic removal was achieved, i.e. 98.3 % for biochemical oxygen demand (BOD) and 85.2 % for chemical oxygen demand (COD), whereas ammonium and total Kjeldahl nitrogen (TKN) removal was 98.5 % and 88.3 %, respectively. Nevertheless, the integration of attached biomass on sponge media helped by significantly improving total nitrogen (TN) removal from 38.7 % to 53.4 % through enhanced denitrification activity of the MBR biomass, even though it was operated under aerobic conditions. Batch experiments confirmed higher denitrification activity (0.58 mg·g-1·h-1) of attached biomass than suspended biomass (0.23 mg·g-1·h-1). Higher first-order nitrification rate was observed in suspended biomass (0.21 h-1) than in attached biomass (0.12 h-1), whereas denitrification rate was higher in attached biomass (0.14 h-1) than in suspended biomass (0.063 h-1). The MBR with sponge media can be considered as an alternative treatment system for controlling water pollution in a recirculating aquaculture system where available land area for wastewater treatment is limited.