+1.
"Though they are omnivorous, rabbitfishes require large amounts of vegetable matter in their diets and are excellent algae grazers. Of the three or four species that commonly make it into the trade, two species are excellent hair algae consumers, making them a real plus in many of today’s aquariums.
The most common in the trade is the foxface rabbitfish
Siganus vulpinus, which can reach a size of 10 inches. Slightly larger and quite similar in appearance (and often misidentified as
S. vulpinus), the magnificent rabbitfish
S. magnificus is another good algae consumer. Both browse on desirable and unwanted forms of algae as if they were cows in a meadow!"
FYI: If you feed them heavily, they won't be as tempted to eat algae, so feed sparingly.
The Dolabella Sea Hare is considered an ultimate hair algae eating machine and cleans every bit of algae mess in your home aquarium. Generally, a four inch hare cleans a 125 gallon reef of all hair alga in about two weeks. On sale here a SWF.com for $9.99. My emerald crab eats hair algae, but not a noticeable amount. Several might make a difference.