The purpose of this book is to evaluate the physicochemical and bacteriological water quality aspect of Lake Ziway in relation to Fish Farming. On global scale water pollution, i.e. microbial water pollution, pose the greatest problem. Chemical pollution is also of a great concern. Twenty grab samples from twenty sampling site ten from the surface and ten from the bottom were collected using Kemmerer volume sampler. A total of sixty samples were collected and analyzed for physicochemical, bacteriological, and heavy metal using standard methods. This study indicated that, there is an increment of nutrient input into this fresh lake system. This may result in the Eutrophication of the lake and consequently deterioration of the water quality in the future. Hence, urgent action is required for the sustainable use of the Lake, before its quality goes behind the turning point.