My Betta Only Swims At The Top Of The Tank :(

[Kkat]

I am new to Betta owning, and fish owning for that matter. In August I got my Betta, George, to take with me to school. Up until early December he was in a regular bowl without a filter or heater. I got him a new 3 gallon tank, it has a log and two plants in it, also has a filter and a heater. But now George only swims at the top of the tank, like the very top and sometimes just floats there. He did swim around the bottom when I first put him in, but now it's only the top. 
 
Is something wrong? He doesn't seem to be bloated, and I have seen him swim to the bottom but he favors floating at the top. If anyone has any answers please let me know

 

[bluesword23516]

How often do you change the water?  

 

[Meeresstille]

Do you have a test kit to tell you the levels of ammonia, nitrite and nitrate? It's a handy thing to have for times where you see your fish behaving strange. Often it has to do with the water chemistry. Since you just added a filter it could very well be a cycling issue, depending on your water changing routine. Also check the temperature of the tank, Bettas like their water to be between 78-82 F (about 25.5 - 27.5 Celsius).

 

[Kkat]

I just changed the water on Monday. I'll have to get a test kit.The temp of the tank has been around 76, how do I warm it up? 
 
Thanks you guys

 

[LyraGuppi]

With a heater.

 

[Kkat]

I've got a heater, it has it regulated at 76

 

[LyraGuppi]

Does it have a thermostat?
 
If not, you'll need a different heater.

 

[Meeresstille]

76 is the low end where you can keep a Betta, I keep mine at 80.