This handy tool will help you more accurately determine the heater you should use for your aquarium. The default setting for difference between ambient temperature and tank temperature is 10° F. This tool is a little more accurate than the 5 watts per gallon rule because it accounts for ambient room temperature and tank size. For larger tanks you may want to consider using multiple heaters to acheive the desired total wattage.
Please input the following measurments in US gallons for the tank
Aquarium capacity calculator
Heater Wattage Calculator
Hex aquarium capacity calculator
Fish quantity calculator
Aquarium Substrate Quantity Calculator
Freshwater Compatibility Chart