I realize I'm mostly repeating what everyone else is saying, but I battled the green monster for quite some time. It almost got me to pack it up. But I followed a friends advice and starting growing and exporting Chaeta in my sump. After that the combination of a good skimmer, snails, a Foxface, a Kole Tang and Hippo Tang seemed to eliminate this stuff completely. I had zero success with Phosban. Hope this helps!