Emerald crab with an attitude

[saltyflash]

I've got 2 emerald crabs with a bunch of snails, hermits, shrimp and a yellow tang. (just started the tank recently so I'm slowly adding)
Lately, after a molt, both of the crabs seem to attack anything within striking distance including digging into hermits shells (with the hermit still there) and attacking large nassarius snails til the snail can slip away. There appears to be plenty for them to eat as they graze constantly and have grown kinda large.
I'm concerned about these guys taking out a sleeping fish or a more passive invert that I might want to add to the tank down the road. I've heard that emeralds can be semi-aggressive but what are the odds to get 2 mean ones out of 2? Thoughts? What about porcelain crabs or strawberry crabs, better temperment?

 

[Swimfins]

There are 2 varieties of emerald mithrax crab, the small and peaceful green mithrax and the larger more agressive red mithrax. MY little green emerald is quite docile. i suspect you have the red variety, not reefsafe.

 

[jessie]

porcelain crabs are great, they filter feed and dont bother anything. i have 2, 1 for over a year. the only problem i have with mine is that i hardly ever get to see them. maybe once every 2 weeks or so, i only get to see both of them at the same time about once a month.

 

[Blinky]

Some ECs are VERY agressive - as SF says, pink mithrax can sometimes be jerks. In addition, if you've got two males that are big and hungry, that could be part of the problem. Even green emeralds can grow up into monsters. I've got a little green female who is an absolutely model citizen, but after losing things to a huge pink male I keep my eye on her just in case she decides to turn into a rogue.

Porcelains are completely reef safe filter feeders, and come in a variety of gorgeous colours. Mine's purple, I've seen some with blue stripes and the more common but very pretty white with brown/red spots.