I hated that stuff! IF it's actually hair algae, not Bryopsis. Which is often misdiagnosed as Hair algae.
So, here's how to tell.
IF it's hard wires of green thread like algae which does not have branches. It's Hair algae.
If it's soft and can easily be pulled off rocks, AND it has tiny branches. Then it's Bryopsis.
IF it's actual hair algae, the only way to rid yourself of it completely is to maintain ZERO phosphate for a long time. (GFO reactor works well)
IF it's Bryopsis, You need to get your Magnesium up to 1650 for a week or so, using Kent marine Tech M. (It'll kill it).
I never found anything that would eat real hair algae, other then my scissors and the toilet.