caseykell21 : According to Dr. Ronald Shimek's book Marine Invertebrates the Mithrax sculptus, or Emerald crab is herbivorous, seldom preying on sesile animals. It does this if it runs out of the adherent fleshy green algae (including bubble algae) it prefers to eat. It is from the Caribbean, grows to a maximum of 2" across the leg span, and is suited to tanks from 10 gallons up. It requires normal aquarium conditions, some rock and algae. Sounds like an ideal animal to me!
Here is what Foster & Smith have on their website:
"Emerald Mithrax Crab
(Mithrax sculptus)
Click here for a larger image
Quick Stats
Care Level: Easy
Tank Conditions: 72-78°F; sg 1.023-1.025; pH 8.1-8.4; dKH 8-12
Max. Size In Aquarium: Up to 2½"
Color Form: Green
Temperament: Semi-aggressive
Reef Compatible: Yes
Diet: Omnivore
Origin: Caribbean
Family: Majidae
The hardy Emerald Mithrax Crab, also known as Emerald Crab or Emerald Mythrax Crab, has a shiny green, flat, compact body and hairy legs.
It requires a mature aquarium with plenty of rock work and hiding places. The Emerald Mithrax Crab eats algae and various types of meaty items it can scavenge. It can be harmful to small fish, but unlike many other animals, it will eat bubble algae and is useful for cleaning tanks of this potential problem. They are an opportunistic feeder, and if food is not available to them, they may turn to supplementing their diet with corals or invertebrates.
If there is insufficient algae, their diet should be supplemented with dried seaweed, chopped meaty items or a quality pellet food.
Approximate Purchase Size: 1/2" to 1-1/2" "