I have a 300 watt one on my 84 gallon. It seems to turn off and on quite a bit so i think a 200 watt probably would have been a better choice. The click is also quite loud when it turns on and off but this may be more noticeable to me since it's in my bedroom. Also the heater is set on 25 and it keeps the tank from 25.1 - 25.3. The temperature dial is also quite loose so an accidental knock could send the temperature skyrocketing. But other then that, I'm quite happy with it. No ugly heater in the tank and no need to get your hands wet when adjusting temperature.