I had a problem with hair algae for about six months. Many people told me that the best remedy for them is "Blue Life Flux RX. I used this product 3 times with strict adherence to the instructions for 3 months, but without a visible effect. In addition to hair algae, there was a little dino and cyano.
When I was already desperate, one of the guys in our hobby in our LFS advised me "API Algaefix", saying that he had a similar situation. And a miracle happened. Within 2 weeks, absolutely everything disappeared: hair algae, dino, cyano, and even the green coating on the glass.
Because of the problems, I rarely populated my tank. Of the living creatures, there were 5 fish, one sea urchin, a Lismata shrimp, about a dozen LPS and several SPS. Neither the fish, nor the corals, nor the urchin and shrimp had any problems. Now this drug is mandatory for me. I add it once a week to control the algae.