Frilly Arrow Crab, Stenorhynchus seticornis is a crab that we only find every once in while. They are also know as Frilly Decorator Crab. They get their name from attaching a variety of things to their body to blend in with their surroundings. They might start putting zoanthids etc on their back which makes them not reef safe in our opinion. As far as food, they can be classified as a scavenger but it is not clear if they would help with any algae problems. They look like and arrow crab but with more algaes etc. on them.
We will try to send you a specimen with decoration on it but they change so much that it is not always possible.