Water is the key, as the saying goes. The koi will thrive as long as the pond is properly maintained. An abundance of factors, many of which interact with one another, influence water quality. However, when discussing water quality in the context of koi-keeping, only physical and chemical characteristics such as temperature, dissolved oxygen levels, pH, and nitrogenous waste created by the fish are of any relevance. There should be a balance between the alkalinity, phosphate content, organic particle count, and dissolved organic molecule count.