A seed rearing experiment was attempted to evaluate the effects of stocking densities in the biofilm-based system reared with pearlspot, Etroplus suratensis on different aquaculture parameters. Pearlspot advanced fry of size (4.67 ± 0.04 cm/1.71 ± 0.03 g) stocked at four different stocking densities viz 50 fish (T 1 ); 100 fish (T 2 ); 150 fish (T 3 ) and 200 fish (T 4 ) m −3 in the biofilm-based rearing system and at the rate of 150 fish m −3 in the clear water fed (CWF) system tanks. The total ammonia nitrogen and dissolved oxygen levels in biofilm tanks with different stocking density were significantly lower than CWF. Diatom was found as dominant plankton in all biofilm treatment tanks in water as well as on substrate. The growth parameters were found to significantly decrease with increasing stocking density in the biofilm-based rearing system. The significant highest individual growth parameters and significantly lowest fish biomass were found in T 1 . Final fish biomass was found to increase with increasing stocking density up to 150 advanced fry m −3 and then reduced due to decreased survival. Body composition analysis of E. suratensis showed increased protein and decreased lipid levels in all biofilm-based rearing system treatments at different stocking densities compared with clear water fed system. The present investigation findings on plankton abundance, growth, body composition and blood parameters at different stocking densities will provide guidelines for selecting appropriate stocking density for pearlspot advanced fry to fingerling rearing in a low saline biofilm-based system without providing a supplementary diet.