Well, the betta's have a personality all to themselves. Tie, unfortunately is sick atm, and is lethargic. I keep mine in 1/2 gallon tanks with gravel and a plant, and them seem happy (they blow their bubble nests). Anything smaller is no good, unless its just a hopital tank. Male bettas HAVE to be separated, and it's sad, but you can get a 5 gal. and put a divider in it and keep two males like that... boy does it look pretty. Even keeping a male and a female together is risky. The male will harass the female so badly that she'll eventually die <img src="/images/graemlins/frown.gif" alt="" />
They are said to be the easiest to take care of, not to mention CHEAP! But let me tell you, when they get sick, it's pricey. Today I bought a bottle of Melafix and 2 bottles of Bettaplus (stress coat) at walmart for 13$. Then I got a bucket to mix a medical cocktail in, and it cost 5$... the list could be endless. But when they stay healthy, they run 4-8$ to buy, and 12$ for a Hagen Betta Starter Kit, which keeps them well
If you want to know more, check out the betta thread on the fish board <img src="/images/graemlins/smile.gif" alt="" />