The present study was performed to assess the effect of stocking densities and seaweed/aquatic plant on water quality, growth and feed utilization of the white leg shrimp (Litopenaeus vannamei) in co-culture. The experiment included six treatments in triplicate. Two stocking densities, postlarvae (PL) with mean initial weight of 0.074±0.014 g were mono-cultured at 30 and 60 PL 120L-tank^-1 or 250 and 500 PL m^-3 considered as controls; the other four treatments were co-cultured system, each stocking density shrimp was integrated culture with red seaweed (Gracilaria sp.) or aquatic plant (Najas sp.). The density of Gracilaria and Najas in all treatments was the same (100 g tank^-1 or 833 g m^-3). The trial was conducted in the static system at salinity of 10 ppt and outdoor condition with plastic shade. Shrimp in all tanks were fed commercial feed to satiation with four times a day at 6:00, 11:00, 16:00 and 21:00 h and lasted 45 days. Results showed that survival of shrimp was not affected by the stocking densities and the culture system, ranging from 97 to 100%. Regardless of culture system, the final mean weight of experimental shrimp in treatments 250 PL m^-3 (3.17-3.41 g) were significantly larger (p-3 (2.63-2.91 g). Growth performances of shrimp in co-culture with Gracilaria or Najas were similar; they had statistical higher growth rate compared to the mono-culture that was observed for both density treatments. Application of the co-culture, feed conversion ratio could be reduced from 23.2 to 28.1%. Moreover, the mean concentrations of NO₂^- and NH₄-NH₃ in the co-culture system were 48.3-75.7% and 50.3-64.5% lower compared to the mono-culture systems, respectively. These results indicated that Gracilaria sp. and Najas sp. can be suitable as good candidates for integrated system with white leg shrimp for feed efficiency and water quality improvement