I used to have my betta in a 12 gallon nanocube. He seemed pretty happy. Interestingly, I had read in articles online that a betta that swims vigorously up and down, side to side is a happy betta. I transfered my betta to a 55 gallon tank, 4 feet long. Boy, the betta would sprint from one end to the other, turn around and sprint back. He would do this several times, then relax for a while. Some time later, he would start sprinting again. The other fish didn't bother him and he didn't bother them. So, while you can't ask a fish if it's happy, some body language can be insightful.
A "betta on patrol" is one thing. "Sprinting" a meter in either direction sounds like a stressed fish, to me. I've used 40-gallons for bettas before, but it was sort of divided (in a natural way). That kind of activity doesn't seem like a very natural behavior.
I'd like to know how a 12 gallon gets off being nano.
The nano is typically in reference to saltwater, not fresh. A lot of nanocubes are used for growing small corals and stuff. And in saltwater terms, 12 is definitely a nano. But some people do use them for freshwater too, but they're still called a Nanocube. Some are a solid square shape, and actually pretty cool looking.
A "betta on patrol" is one thing. "Sprinting" a meter in either direction sounds like a stressed fish, to me. I've used 40-gallons for bettas before, but it was sort of divided (in a natural way). That kind of activity doesn't seem like a very natural behavior.
I can certainly see this point of view. He lived for years and my water chemistry was always near perfect (7 parameter water tests). He was never bullied, either. So, not sure where the stress would come from. He just took his occasional jogs around the tank. After about 3 years, he went up to the fish bowl in the sky.
Check out the eBook Betta Fish Care Made Easy
Similar Threads
what? not good enough for you? 
