Choosing the right aquarium heater involves considering: Room TemperatureAquarium Water VolumeDesired Temperature Allocate 2.5 to 5 watts of heating power per gallon of water in your aquarium.For instance, a 10-gallon aquarium would typically require a 25- to 50-watt heater.In colder rooms, opt for a more powerful heater, potentially exceeding 5 watts per gallon, to effectively warm the tank. Indicator & Dual Temp. Display Red light indicates active heating, blue light signals temperature maintenance. Digital display shows current & target water temps. Easy Setup One-button operation adjusts temp by 1°F. When the temp reaches 93℉, pressing the button again will reset it to 59℉. Hold button 5 sec. to switch between ℉ and ℃. Suction Cups Conveniently attach the fish tank heater securely to tank walls using included suction cups. Comprehensive Preparation for Unforeseen Circumstances Dry Run Protection Error code (E1) activates if the fish heater not fully submerged. Submerge to clear code and resume proper functioning. Overheat Protection Heater auto-stops(displaying "HH") if over 95°F/35°C, resuming when the water cools below 93°F/34°C. Memory Function Thermostat retains last temperature setting after power outages, ensuring the turtle heater resumes previous operation upon restoration.