I'm going to commit heresy here. I'd suggest bumping your nitrate up a bit, but trying to keep you PO4 where it's at. Also, how much flow does that area get? Sometimes algae can become self-sustaining if you have a lower flow area and stuff settles where filamentous algea types grow. The stuff that settles around the base of the strands provides nutrients. Change filter socks or floss often, baste areas with low flow and to get the mulm off of the rocks. I run at 0.1 PO4 and 10ppm NO3 and have found that sweet spot works very well for me. I have algae in my tank, but I have to look very hard to find it and scrape my glass maybe every 4 days or so. I also run a big bag (a liter or so) of seachem matrix in my rear chamber - well, actually it's approximately half matrix (pumice) and half crushed coral. I dose some prepared bacteria into that side maybe once a month and I use several different ones with different bacterial strains to try and maintain diversity as well - just a few ml basically when I remember to do so. I also run UV constantly - it's always on except after I dose bacteria when I keep it off for a day or two. These are things that have worked for me. I also vacuum the sandbed one small section at a time when I do my very rare waterchanges - helps to prevent crud accumulating too much. These things work for me and have done so in multiple scapes in my current tank. When I let thigns get a bit out of hand once and my nutrients got too low, I get some hair algae, but I just got my nutrients back in line, and followed the basic principles above and it was gone within 2 months.
I loved my ninja star astreas, but they really did not eat any filamentous algae at all. They also tipped over a lot - if I caught it in time and flipped them back over they would go on their way. I lost all three of mine that way - not catching it right away. Really cool looking snails, and great at cleaning up spot and film algae on the glass, and pretty good with the diatom-type brown dust stuff. Only critter that ever went after filamentous types for me has been a tuxedo urchin, and it is dang good at it.
