my twenty gallon tank recently experienced some kind of disease that litterally killed of my fish overnight so all that was left was my baby spiny softshell turtle named timmy. i noticed in my sisters room that she had her betta in a lil jar so i just chucked that lil sucka in my 20 gal. and within minutes his color almost doubled in brightness. so im guessing that he is much happier in a twenty gallon. i kno most people wont waste money on a 20 gallon for a betta but this lil guy got lucky. he probably hadnt been in anything bigger that a gallon his whole life. 