Killer Emerald crab?!

[Sir Alex]

That looks like a male emerald. Males can get very mean. All the emeralds in my tank are female & excellent cleaners. I would get another emerald if I was you, just make sure its a female. Females have & keep tiny claws FYI.

You can identify crabs by the aprons on their bottom. The females have a much wider ones.

And are porcelain crabs so aggressive?