Nope, Bala's are out of the question they need at least 6-8 feet of swim room. VERY jumpy fish... They love to dart across the tank so they need tons of room. They slow down when older BUT they also get 14" long but the common size is around 12". Still I would only have them in an 8 footer IMHO. Thats just how I feel but you may different. Plus they would get stressed too easy, if aggression is directed on them they begin to hide in corners, you'll never see them and they will sometimes float on their sides under stuff. A GT will deffinately stress them. Danio's are just stupid so they can't remember far back enough to remember they were being chased. Aggression never really affects them too much.
GT's can be VERY VERY aggressive so watch out. There is a 3.5-4" one at my LFS and is insane. Flares up and flips out when you come near the tank trying to bite you. Love the little guy and I think I am getting him.