The degree of accuracy and constancy of cooking temperature required varies with the food cooked. In some cases it is not critical. A 15 millimetres (0.59 in) thick piece of fish will cook in 17 to 18 minutes at any temperature from 44 °C (111 °F) to 61 °C (142 °F).[8] Such food can be cooked in a switched-off slow cooker filled with hot water and a thermometer.