Betta floating at top

[ibndaisy]

Hello there. I think I might have a problem with my Betta fish. I have had him for about a year now. I regularly clean his tank and do water changes. However, in the last week, he's just kind of been floating around at the surface of the water. He will swim to the bottom of the tank, but as soon as he stops waving his fins, he just bobs right back up to the top. Sometimes, it even seems that he is rotating onto his side and resting along the wall. Is there something wrong with him? thanks!

[imma24]

Questions:

What size tank are we talking about?

Do you test your water parameters? How often do you feed your fish & what are you feeding?

[Tiari]

Same questions as above :), as well as what temp are you keeping the tank at?