Catherine, don't give up the battle as I said earlier it takes a lot of patience and perseverance. i still insist once it takes hold it needs very little in the way of nutrients to survive.
When I had the hair algae and it was really bad, you couldn't tell that I had any rocks they were so covered. (For some reason my camera always goes missing when my tank looks really bad
) I finally fought the battle over the long term by letting the algae grow really long (it is easier to manually remove when its long) siphon it all out and then place all the crabs, snails and urchins directly onto the short stubs that is left.
It took a long time for me but eventually I won... only to be taken over by dictyota but thats another story