Probably but you couldn't have the tropical fish. If you live in a tropical climate though, then it wouldn't be advisable without the opposite of a heater, a cooler.
yeah you could, but goldfish need lots of space and are astonishingly messy,
also i know goldfish can harbour some diseases with no ill efects that can kill tropical fish, maybe the opposite is also true, so a thorough tank clean might be necessary first...
