Emerald Crabs(Mithraculus sculptus) are a valued member of CUC’s for their love of bubble algae. This species of crab is native to Caribbean waters, and is characterized by their green color. They are omnivores and in addition to taking care of Valonia ventricosa, they will also help remove uneaten food waste in aquariums. If they run out of things to eat, their diet can be supplemented with seaweed (nori) or meaty foods like shrimp. Don’t be surprised if they seem to have disappeared once they are added, as they are nocturnal, and tend to stay hidden among the rockwork. These would be considered a medium sized crab as they max out at about 2.5 inches. Make sure to monitor water chemistry, especially calcium, and iodine as those are elements necessary for them to have successful molts. Prior to adding them to reef tanks, make sure to slowly drip acclimate them as they are sensitive to fluctuations in water parameters, and they cannot tolerate copper, so avoid copper based medications.