Originally Posted by raerae4u2
Maybe I'm wrong, but I just use common sense. I would think that more room means a happier betta;)
Yes, this is true for the most part. Many bettas do seem to prefer larger tanks with lots of swimming space, but I have heard of a few who've done better in smaller spaces. It's all trial and error until you find what works best for your fish.
I think it all depends on the personality of the fish, too. My 3 are all perfectly healthy in 1 gallon tanks, and couldn't be happier