SUMMARY Brazil has favorable hydrographic and climatic conditions for the development of fish farming. The success of this activity depends on the quality of the water, since it directly influences its productivity. Therefore, in order to verify the microbiological and physico - chemical characteristics of the water in the creation of the tambaqui (Colossoma macropomum) species in fish farming in São Bento, a municipality located in the. State, 16 water samples from six fish farms were evaluated for the physical parameters (Temperature, transparency, dissolved oxygen, pH, turbidity, color, alkalinity, hardness, nitrate and nitrite) and microbiological (coliforms and heterotrophic mesophilic bacteria). According to the findings, all samples were contaminated by total and thermotolerant coliforms, 13 (77.15%) were outside the standards recommended by the legislation. As for the mesophilic aerobic heterotrophic bacteria, the mean counts ranged from 30.6 x 102 to 4.7 x 104 CFU / mL. As for the physical-chemical parameters, it was verified that the temperature ranged from 27.4°C to 30°C; PH 5.0 to 8.2; Transparency ranged from 0 to 46 cm; Turbidity from 12 to 1,251 NTU, the color from 0 to 666.50 UH; Dissolved oxygen from 7.1 to 14.7 mg / L; Alkalinity of 17.5 to 412 mg / L; Hardness from 14.6 to 1027.8 mg / L; Nitrate from 1 to 160 mg / L and nitrite from 0.01 to 0.45 mg / L. The findings show that the water of fish farms has inadequate microbiological and physico-chemical characteristics for fish farming.