I have a betta in the same tank (heated 3g Tall) and he's very happy, he's been in there for almost a year now but before that he was in a 50g with many other fish and before that he was in a 5g with a few neons. He's been around for a while now
We've had him for 3 years this january. He fights with his reflection alot but I think it's to pass the time
I also agree about the little puffers, they are very cute! Perfect for a litthe tank.