Who eat's Green Hair Algae??

[naesco]

Either too much light or poor water quality which is the root of your problem

In the meantime order in a sea hare.
Make sure you acclimate it very carefully or it will not survive the stress of transfer.
Getting it from a fellow reefer is best.
Once you get it and it is down to 90% of the hair algae eaten you need to start feeding it spirulina sinking tablets or sink some nori to the bottom or it will die of starvation.
It is best to pass it on to another reefer who has an algae problem
The other fish solutions are hit and miss and not worth disturbing your existing fish for.