Manual water tank heater hose: see update in first post

I'm not going to get in the middle of this dispute -- I have seen it before. But all I know is that if my water tank is really cold and about to freeze, it can't hurt to add some hot water, right? If that is not true, and I should add ice cubes to the tank to keep it from freezing, I am out of luck -- ice cubes won't fit into the fill tube. ;)