I have one at home! They DONT like the cold, their metabolism slows right down, they barely eat, sleep all the time. Need to keep the water at at least 22 degrees, which im finding hard at the moment. Also, dont just feed them the little flake feed from the pet store, they need those freeze dried small dead worms as well, after all, they are carnivores. Youll have to change the water around every 3-4 days too. Dirty little buggers.
http://en.wikipedia.org/wiki/Betta