Abstract: The present study was aimed at investigating the relationship between carbon source concentration and nutrient uptake efficiency of three protozoan isolates. Three carbon sources (acetate, glucose and sucrose) were used at respective concentrations of 5, 10 and 15 g L-1 for this investigation. The study was carried out in a shake flask at a temperature of 25°C. Aliquot samples were collected at time zero and every 24 h for the estimation of phosphate, nitrate, Chemical Oxygen Demand (COD), Dissolved Oxygen (DO) and growth rate. Results revealed a significant phosphate and nitrate uptake at carbon source concentration of 5 g L-1. This was irrespective of isolates or carbon source used. The results also showed that with a high initial carbon source concentration, initial COD was observed to be high. In the presence of acetate, COD removal from mixed liquor was not observed. However in the presence of glucose or sucrose, COD decrease was observed. There was no observed significant variation (p<=0.05) between DO values at the different concentrations of carbon source. A similar trend was also observed for growth rate. This study had been able to give an insight into the optimum carbon source concentration in mixed liquor that will enhance nutrient uptake by the test protozoa.