Bacteria from stagnant water, coloured scanning electron micrograph (SEM). Stagnant water is ideal for breeding of bacteria of many types. Bacteria prefer to breed in areas that are unclean and are often within a certain temperature range. The Legionella bacteria capable of causing Legionnaires' disease will multiply in a temperature range of 20-45 degress celcius. Dysentery, cholera and botulism are all caused by bacterial contamination of stagnant water. Magnification: x5000 when printed at 10 centimetres wide.