For this, DM values were used, N and P contained in the tilapia reported by Tian, Li, Dong, Yan, Qi, Liu and Lu (2001). For the sludge produced calculation was determined the dry matter ratio as DMR = FCR * (% DM in feed/% DM in tilapia). This data were necessary to determine the waste production rate as: WPR = (DMR _ 1) * (% DM in tilapia/100) (Boyd et al. 2007).