We acquired a male betta from a friend who tried having him in with a goldfish. The goldfish was getting eaten up, so she called me & we wound up with the betta.
At first I bought a .5 gallon tank. It was small, but bigger than many of the tanks they tried to get me to buy at the pet store. I got online & found this forum where I read about them needing a bigger tank. My betta was barely swimming around & just kind of "hung out" in the .5 gallon tank.
After moving him to a 2.5 gallon tank, I can say that my betta is now happy!
He swims all over the tank, loves to play around the filter, swims through his rock bridge & swims right to us whenever we peer into the tank. There's no doubt that to have a happy betta, it needs a larger tank!
Thanks to all the posters in the forum that helped educate me about just what my betta needed.