My sister has a betta...she lives in the room adjacent to mine. My rooms is always warm and stuffy. Pretty good for a 1 gallon with no heater...My sister's room is always cold and breezy (with window open, when closed a chill is felt). Her betta is in one of those cube things sadly and i touched the water and it was freezing probably below 70. I quickly put him in my room. I just don't feel good for him. He is much smaller than my betta and less active (cus hes frozen). I stole him and put him in my room for now because the poor guy deserves at least warmth...I dont know..I just feel horrible. She wants to get another and put them in a 5 gallon (divided). Thats fine but she hates taking care it now so how will she feel with two?..I just feel bad thats all.