Here is a read on cloudy glass: http://www.ha.com/tips-for-cleaning-cloudy-glass.s
And another: http://en.wikipedia.org/wiki/Glass_disease
And another: http://en.wikipedia.org/wiki/Glass_disease
Glass doesn't cloud from the inside, you are mistaken about something.
It's likely the answer has already been said, but what about is there a protective plastic cover you never took off?
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If its only on the front pane, are you able to turn the tank around and make the front the back, and the back the front?
Here is a read on cloudy glass: http://www.ha.com/tips-for-cleaning-cloudy-glass.s
And another: http://en.wikipedia.org/wiki/Glass_disease
