Fluval 200 stuck on 77°

[Trop65]

My 65 gallon tank with a 200w Fluval heater will not go above 77°. The blue light stays on, not flashing. It is set for 80°. Placement is right next to the intake tube, vertical. The room temp is 68° (winter here).
My question, should I bump up to the 300 for a tank this size? Or is the heater flawed?
I got it 3 months ago and until recently it has been at a steady 78°, green light stayed steady. I do unplug it during water changes.
Thanks much!

 

[Archerfish]

Your heater is undersized for the desired tank water temperature vs. ambient room temperature. You want to raise your tank's temperature nearly 10-degrees Fahrenheit. A 200-watt heater just can keep up with that much demand. Turning up the thermostat will not resolve the issue. I recommend you acquire an additional heater in the 250-300 watt range. Use them both during the cold months. Make sure there is plenty of water movement around each heater. I use two heaters in my Archerfish tank during the winter. One at each end of the tank with plenty of water movement.

 

[seangee]

I agree with having 2 heaters. Its a partial insurance against heater failure in the winter months and all my tanks have 2.
Personally I also have insurance against fish soup (thermostat failure) in all of my tanks but that is a separate topic.