Red algae, or Rhodophyta, is one of the largest groups of marine algae found in tropical waters. Arrow crabs eat red algae species found in their habitat, including members of the genus Acanthophora, often pale pink and soft: Dasya has soft feather-like branches, and Hypnea is rosy-red with terminal branches that are hook-shaped. Red algae contains the pigments phycoerythrin and phycocyanin.
Green algae, or Chlorophyta, that are part of the arrow crab's diet include species of the genera Acetabularia, which are umbrella-shaped and only found in shallow waters; the soft and hair-like Batophora; Caulerpa; Ulvaria; and Dasycladus. The color of green algae ranges from dark-green to yellow green. Chlorophyll is the dominant pigment in these algae.
Brown algae are members of the division Phaeophyta. Most live in shallow marine waters. Brown algae can also be part of the arrow crab's diet, including species of the genera Colpomenia, which are occasionally found floating free; Dyctiota, light-brown and bushy algae; Lobophora; and Padina. However, the most common genus of brown algae found in the arrow crab's habitat is Sargassum.
Arrow crabs are common in shallow waters with a depth range from 10 to 130 feet. They prefer rocky habitats, generally close to coral reefs. Arrow crabs are only found in the Americas from North Carolina to Brazil. They use coral crevices for shelter, where they spend most parts of the day. They are also found among sponges, anemones and urchins.