Green algae is green spot or slimy? I have seen brown circles of algae in my tanks before, I have decided they were brown algae, if we are talking about the same thing, it wipes off easily? I have also seen brown string-like algae on the plant leaves of my newly setup tanks, or attaching to the glass in tiny strings, but they usually go away with time and water changes. It looks different then the brown algae that blankets the leaves. Just what I saw in my tanks, if it helps, and I found out that if you overdose with sulfur based water conditioners, like Prime, which I did, this can contribute to brown algae.
I like your tank btw, always liked those 54g corners, and like the way you scaped it with the rocks, should look really nice as a contrast to the wendtii.