The study was performed to assess the effects of different feeding rations on growth and feed efficiency of the black tiger shrimp (Peneaus monodon) co-cultured with red seaweed (Gracilaria tenuistipitata) in tanks. Shrimp was mono-cultured and fed commercial feed (CF) to satiation considered as a control and the five other treatments, shrimps were co-cultured with red seaweed (1 kg m-3) and received CF at 100%, 75%, 50% and 25% and 0% feed ration of the control. Juvenile shrimps with mean initial weight of 0.46-0.51 g were run in triplicate and stocked at a density of 100 ind. m-3, and at salinity of 15 ppt. After 60 days of culture, water quality parameters in terms of nitrogen compounds (TAN, NO2-and PO43-) in co-culture tanks were significantly (pmoisture, protein and ash were similar among treatments except lipid content was significantly lower and red coloration of shrimp after boiling was markedly darker in co-culture than those in the control. These results indicated that co-culture of P. monodon and G. tenuistipitata with reduction of feeding ration up to 50% satiation resulted in improvement of growth, feed cost, and shrimp color as well as maintain better water quality in the culture tanks.