This article is from the Aquaria: Disease, Algae and Snails FAQ, by Elaine Thompson, Thomas Sasala and George Booth
Grows mostly on plant leaves as separate, short (2-3mm) strands.
Considered normal. It might be a less "virulent" form of "beard"
algae. Easily controlled with algae eaters such as black mollies,
Otocinclus, Peckoltia and siamese algae eaters.