Is this green hair algae?

[molotov]

I'm going through the same thing right now, except that my hair algea problem is of epic proportions compared to yours. I'm also using RO/DI water and have been running GFO in a reactor for the last week. I tested for phospates and the test came back as 0 as I expected because the algea is absorbing all the phospates

What seems to be working for me is the addition of 10 Turbo Snails and 30 hermit crabs. The snails are devouring it. Hopefully the GFO will help as well. Also I got some Cheato so hopefully that will help absorb some of the phosphates that the hair algea needs.

I suspect the root of my problem is my dry rock leeching Phosphate. I also did not acid bath my rock which I found out later maybe I should have done. I would suspect your rocks are leeching phospate as well. I think with time it will go away. So get some turbo snails and that should help. I also read that sea hares devour the stuff as well.

Good luck with your battle.