I'm a bit skeptical - as I think the concept is similar to the Junior heater at Walmart - which is a warmer...not temperature controlled. It keeps raising the temp within it's power...so, in a warm office, the tank would be quite hot, and during the evening, if the office gets quite cold, it wouldn't have the power to keep the temp consistent. The Junior heater was ok for a Betta in a 5 gallon Minibow, but still got too warm during the day.