Until recently, I've struggled for years with hair algae issues, even while running a an algae scrubber (which did help, but not cure). I had a destabilizing event (my fault, lesson learned) with an algae bloom a couple months ago and lost some coral. I decided to try Vibrant and over time it has worked amazingly well.
My point of al, that is that for as long as I can remember my phosphate has always tested zero and nitrates 0-.2. With the algae almost gone (the scrubber still grows it, even with the Vibrant) phosphate reads something under .1 and nitrates 5. My surviving coral looks pretty happy.
It makes sense to me, but I was still pleasantly surprised to see it in action.