To manually remove this algae you may pull it, tooth brush it or scrub it off the rock easily. This may work better if the rock is out of the water.
To remove this algae using a clean up crew you may use hermit crabs, turbograzers, sea hares, emerald crabs and urchins. Yet even with a clean up crew it may grow back fast.
You may now try to identify problems that may cause this algae in the first place, hereby you may be able to prevent it rather than cure it.
Problems such as phosphates, nitrates, iron and potassium can make this algae grow. RO water for top up is a must.
Your best bet to preventing this algae from taking over is to maintain weekly water changes, apply good husbandry on your filtration and perform manual/natural algae removal as it grows.
magnesium and alkalinity levels that are in check may discourage green hair algae.
To starve the algae is another option, do this by using filter media in a bag or phosban reactor or a macroalgae like chaeto to reduce nutrients. Increase the frequency of your water change routine, taking the opportunity to siphon out as much hair algae as you can each time.
Old light tubes tend to drift towards the red spectrum, and fuel the growth of hair algae so consider replacing them if they are old.
