Mmm, kind of hard to distinguish from your picture but looks like Fuzz Algae to me. You had weak light and too much nutrients. In my experience nitrates over 20ppm and low light favors Fuzz algae. Get everything back to normal and it will slowly go away with treamming. Keep an eye on nitrates in the meantime.
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Last edited by vanostav61; 05-23-2020 at 03:56 PM.