The objective ofthe present research was to evaluate phosphorus in diet for pacu (Piaractusmesopotamicus) juveniles on water quality, livestock performance, bodyyield and carcass chemical composition. A total of 100 juveniles, 25.9±1.32g average weight were randomly assigned into 20 fiberglass tanks, with fivetreatments and four replications. The fish were fed four times a day (8 and11 a.m.; 2 and 5 p.m.), with extruded diets containing 0.40; 0.55; 0.70; 0.85and 1.0 % total phosphorus. No differences were observed in water quality parameters,except for the concentration of orthophosphate in water, which presented linearincrease. The parameters livestock performance, body yield and carcass chemicalcomposition showed no differences for the levels of supplementation of phosphorusin diet. The use of 0.40% total phosphorus meets the requirements of phosphorusfor pacu (Piaractus mesopotamicus) juveniles, in addition to releasinglower concentration of orthophosphate in water.
