It should be possible in theory at least. A lot of the glass-fronted shops routinely get graffiti scratched into them, And then get it polished off. -If you look at the glass at a low angle, you can see the distortions from the uneven surface, but it looks pretty normal straight on.
I don't know how difficult this would be, or whether it would be cost effective (vs. buying a new tank).
If it's just a light haze, you probably wouldn't need to polish anywhere near as much.
Good luck, and let us know what happens if you try it.