So I got some help from a few of you and have identified my "green leafy thing" as ulva / sea lettuce.
I have noticed it in a few spots and believe it got introduced when I added my refugium with chaeto.
I have a yellow tang and a flame tail blenny.......one spot of it stays trimmed down, not sure if they have found the other spots. not even sure who may be eating it.
Anyway, is there anything else I can do to ensure it stays in check?