Possibly, but that heater is set up to heat five gallons or more. The amount of heat required to warm a 5 gallon tank to that temperature will raise the temp in a one gallon higher than it would in a 5 gallon. I have a 25 watt heater on a 5 gallon tank and I still have to keep a close eye on the thermometer to make sure that when the house warms up, the heater doesn't make the water temperature spike. In a one gallon, I can imagine it would be even worse. It's up to you, but either way, be sure to purchase a thermometer for your small tank because heaters in small tanks require close monitoring to make sure they don't cause rapid changes in temperature that will hurt your fish.