I don't think you have algae at all. It sounds like Cyanobacteria aka blue-green algae. Post pics to confirm. If so, Erythromycin is the answer. However, don't go dumping EM tabs in your tank until you confirm that's what it is.
Post a pic, the type of algae will determine the course of action. It does sound like a cyano out break, which can be solved pretty easily with extra co2, or excel doses.
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