I have this green algae growing in my tank. I don't know where my phosphates and nitrates are but I do run GFO and have an oversized skimmer. TDS is 0 on the RO. I know, for the most part, how to deal with outbreaks but this one seems different. It doesn't appear to be GHA because its hard to pull off, flat, and looks like lettuce. Any idea of what it could be and how to fight it?