From Reefs2go.com:

Friday & Saturday ONLY


100 Blue Leg Hermit Crabs = ONLY $20.00

The Blue leg hermit crab is a reef safe hermit crab which eats algae and left over food.
It is a nice addition to the aquarium as this crab stands out with it's bright blue legs.
They are an omnivorous bottom feeder which has been photographed eating red slime algae aka blue green algae aka cyanobacteria.