If the fuzz looks like a soft beard or like a brush and is greyish in color, its algae. A few fish are known to eat it - Siamese algae eaters, barbs, mollies....of which the SAE is your best bet.
You also need to address the root cause of the problem - nitrates, phosphates due to too few water changes or excessive feeding. Increasing the lighting might also help as the plants will grow faster thus competing with the algae.