We still don't have the filter on...will be going to the store later this afternoon. Ever since the filter has been off Angus has been making a massive bubble nest. Like all night and today. He's on a mission! lol
Lol, make sure it isn't just his normal oxygen bubbles. Sometimes when the filter isn't on, a weird film covers the top of the water. This will end up trapping normal oxygen bubbles into it.
Lol, I'm sorry. I got really excited about my betta in his 2 gal doing the same thing. Then it occurred to me that there was a film at the top of the water trapping his oxygen bubbles in place. Technically it isn't oxygen, but carbon dioxide. Still, lol.