I've used body shop rubbing compound
to take some of the mineral deposits and cloudiness away from glass. My tanks were empty at the time, so that might not work if you have water in the tank.
I've also used rubbing compound (medium grit) on my glass versa tops and it removed a lot of the haze. On the really old ones (20 years old) the glass is permanently etched by the mineral deposits and the haze doesn't come off with anything - vinegar, muriatic acid, razor blade, steel wool, etc.