I've heard turbo snails do a good job on algae, but they are huge and will push over smaller rocks.
That nitrate level at 40 is a problem. I'm not educated enuf to know if it feeds the hair algae, but it is too high. What are you feeding and how much? That or too many fish (or a combination of both) can add nitrates. Or insufficient mechanical filtration (skimmer). How often you doing water changes?
I'm not even sure it's hair algae. Looks too formed to me. Got a distinct center and everything. May be just a another macro algae growing. Still, the nitrates gotta get better.
"Life may not be the party we hoped for but while we are here we might as well dance!"