Yeah, it would work less, but cycling is turning on and off, not being on constantly. 50 watts on a tank that needs 100 watts wouldn't cycle at all, it would be on constantly. So would 100 watts. 150 would turn on for a while, then off for a little while, on for a while, off. 200 would be on for half as long, off for the same amount of time. 250 would be on for 1/3rd the time, off for the same amount of time. Uhhh...Anyway, the closer you get to the exact number the longer the heater will be on and the less it will cycle. That being said, I have 300s in all my tanks.