I would say it's Staghorn.
http://www.aquaticscape.com/articles/algae/staghorn.jpg
I didn't find any info on algae eaters that would take care of it but I did find this small article.
Staghorn algae:
Looks like individual strands of hair algae but tends to grow in single branching strands like a deer antler and is grey-green. Seems to grow mostly on tank equipment near the surface. Difficult to remove mechanically. Soak affected equipment in a 25% solution of household bleach and water to remove it.
The website made recomendations for algae eaters that could take care of other algaes but made no such recomendations for staghorn. Perhaps somebody else may have another suggestion.