Good heater for a Fluval Spec V housing a single Betta?

Just got my first betta today. He's in a Fluval Spec V in my office. I originally set it up with a 25W Aqueon heater (and stuck the heater right next to the filter outflow tube).

After I bought him and went to the office to acclimate him, I realized that office heat is kept lower on weekends, as temp was down to 76. I'm guessing a 25 watt may just not have the power to keep a 5.6 gallon at 80 degrees if the ambient temp is 60? Anyone have any suggestions? Is a 50W overkill, or is there a "better" 25W that will be able to hold the temperature over the weekend?

He didn't seem to mind 76 all that much, but long term, I'd really like to keep him at 80.

 

For a 20 degree difference, you may need a 50 watt. Just pay attention to the tank temp; if the room temp increases dramatically, the tank may get too warm.

 

50w is definitely not overkill, just invest in a good heater because it has to be able to monitor the temperature well and not overheat the tank.

 

I used a hydor 25w for my 2.6, it was perfect. But since it gets a bit chilly in your office, I agree with getting a 50w.

 

Now I'm not so sure...the past two days, the 25w (at least during the day) easily gets the tank up to 80-82. Is there a greater chance of cooking him with the 50W? I'm also concerned about the constant temperature fluctuations.

 

I think the problem was that was I had no water flow in the compartment housing the heater (next to the filter outflow tubes). I poked a few big holes in the tube, und upgraded to the 50W, and suddenly now everything seems fine.