Two "streaks" running down my tank.

Jan 20, 2005
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Missouri
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#1
On my glass 40g, there are 2 streaks running down on one end. They really aren't THAT noticeable, only if the glass is viewed at an angle. They look like water streaks but clearly are not. They do not come off with windex or even bleach. Anyone know what they may be, or even better, how to get 'em off?