Background: In recent years, Lake Kossou has been subject to heavy human activities, including clandestine gold panning and the extensive application of nutrients related to the repetitive fish farming activities of the fish farm in floating cages on the lake. Objectives: This study thus aims to evaluate the influence of fish farming activities on the ecological quality of the waters of Lake Kossou on the basis of physico-chemical parameters. Methodology: The physico-chemical parameters of the waters of the floating fish farm on Lake Kossou were studied on a seasonal basis between 12 May 2017 and 26 February 2018. In-situ measurements and chemical analyses were carried out on water samples taken from 0 to 6 m deep in the lake waters. Results: Analyses show that the waters of Lake Kossou have a low transparency ranging from 0.62 to 1.5 m with high nitrate concentrations ranging from 0.82 to 7.02 mg/l. The two main seasons were characterized by high values of temperature, pH, nitrate and dissolved oxygen content. The stratification of temperature, pH, dissolved oxygen and nitrate content revealed the presence of a metalimnetic layer at a depth of 2 to 3 m in Lake Kossou. Conclusion: Data obtained from nutrient salts and transparency therefore characterize the advanced trophic status of Lake Kossou.