The rena smart heater has anelectronic sensor that accuratley monitors the temperature which can be set from 20 34 degrees celciusr the heater incorporates a warning light to alert the fish keeper to any undesired temperature change the light will flash fast if the temperature is 3 above and when the temperature is 3 belowr a huge benefit of the smart heater is that it is unbreakable made of composite materials the smart heater is insensitive to mechanical or thermal shocks safe to handl