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Background: Sub-lethal toxicity bioassay experiments were conducted to determine the toxicity of glyphosate herbicide on Koi carp, Cyprinus carpio fingerlings. Koi carp fingerlings with mean length 8.06 ± 0.99 cm were obtained from a freshwater fish seed hatchery of the university.Methods: The fishes were exposed to sub-lethal concentrations i.e. 1/10th (3.6 mgL-1) and 1/5th (6.6 mgL-1) of glyphosate. Oxygen consumption rate, Ammonia-Nitrogen excretion rate, Oxygen:Nitrogen ratio and food consumption rate were recorded after every 7 days for a period of 28 days.Result: Results indicated significant decrease (P less than 0.05) in oxygen consumption in 1/10th and 1/5th of LC50 concentrations. Ammonia-Nitrogen significcantly increased in exposed fishes. Oxygen : Nitrogen ratio and food consumption rate also significantly decreased (P greater than 0.05) in treated fishes. The results indicated that glyphosate had impacts on exposed fish, hence, the need of regulation of its usage to protect non-targeted species and the environment.