Algae can interfere with treatment processes at a water treatment works. Coagulation control is critical to reduce the impact of algae on downstream processes. This paper investigates the coagulation and flotation of four species of algae - Asterionella formosa, Melosira sp., Microcystis aeruginosa, and Chlorella vulgaris. The zeta potential at optimum removal was measured and it was observed that when the zeta potential was reduced to between -8mV and +2mV, removal of algae and associated organic material was optimized, irrespective of the coagulant dose or pH. Process control using zeta potential is therefore a viable tool for algae removal.