Red Decorator Crab or Spongy Decorator Crab, Marcocoeloma trispinosum is a crab that we find every once in while compared to their gray cousin. Their stunning coloration stands out in every aquarium. 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.