Die Algae!

A large ammount of algae eating (Amano shrimp Caridina japonica ) would take care of your problem. If you can buy them and there aren't any fish in your that might eat them, i would suggest getting 20 or so Amano shrimp. They eat hair algae quite nicely.
 
not sure for somethin like that..... i would just put a temporary sae or somethin in there then put it in a different tank later on after its gone
 
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