Those look like aptasia to me. Are they individual things that retract when touched? Hair algae has more of a matt look to it. Those things look long and flow-ie. If that stuff retracts when you touch it then you have a serios aptasia problem. I would take each rock out and scald it, wait a few weeks and take another. Hopefully you'll make it around the horn before they take over any more of your tank.
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