Emerald crab question

[pocilipora]

Im not convinced that these were Emerald crabs. He said he may have at least 6 of these in his tank. He didnt say he bought them at all. 6 Emerald crabs just happened to be on his live rock when he bought it... come on. What I can see is them being another type of crab just feeding on dead or dying live stock. Id say your safe buying an Emerald crab, but it is hit and miss as to weather or not they are going to eat the algae you want them to.JMO