Abstract: The physico-chemical water variables of water samples contaminated with a mixture of the Water Accomodated Fractions (WAF) of dispersed and undispersed phases of Bonny Light crude oil at sub-lethal concentrations of 0.2, 0.4, 0.8 and 1.6 mL L-1 were analysed to assess the effects of these mixtures on the water quality of the test media containing a fish, Oreochromis niloticus. These were measured against a control. The temperature, pH, DO, TDS, conductivity and redox potential of the test media were significantly affected (p<0.05) by the presence of the mixture especially by the dispersed phase at the different concentrations and these were positively correlated.