Before turning on the machine, you should check whether there is any damage to the product, fix it according to the regulations, and then turn on the power to adjust the temperature. If there is damage, please stop using and please feel free to contact us. The fish tank heater should be completely immersed in water, the temperature controller can not be put into the water. When cleaning or maintaining the aquarium heater, please turn off the power for 5-10 minutes before removing it for cleaning.