I purchased two types of hermit crabs, scarlet reef and red tipped. Upon placing them inside the aquarium, they went nuts. One of them realized there was food first, and mowed down the algae through the sand.
The others climbed onto the rock and mowed down the hair algae.
It took about three days until I had to supplement the tank. They pretty much destroyed all the alage available.
Foster & Smith offers an algae attack pack with them: http://liveaquaria.com/product/prod_...0&TopCatId=420