Water turbidity (A) and biological oxygen demand (B) for water inlet (Inlet) and effluent from fertilized (Fert) and unfertilized (NoFert) ponds where tambaqui Colossoma macropomum were reared for 10 months. Lowercase letters indicate significant differences between Inlet and Fert; uppercase letters indicate significant differences between Inlet and NoFert; and an asterisk (*) indicates significant differences between Fert and NoFert (Anova test, P < 0.05).