Emerald Crab becoming full on predator?

[Thomasflynn15]

So I have the emerald crab that is almost the size of the palm of my hand. This morning I found it shredding apart my orchid dottyback. I hear these guys can get pretty destructive as they get bigger and older can they potentially become predatory to the point where they grab your fish out of the water column?. The body looked freshly killed, still bright purple not faded as if it were dead an decomposing prior

 

[Sharkbait19]

Anything is possible with an emerald that size (especially considering the dotty is a rock dweller), but they are primarily herbivores and fish are able to swim away so I’m skeptical of any emerald crab kill.
What else is in the tank and what was the most recent addition? Usually something else is at fault in these scenarios.

 

[ss30]

It's possible that the fish was on it's way out. It's like when you here people say that their fish was stuck to the back of the power head the chances are that it wasn't 100% healthy.

 

[Thomasflynn15]

I have had a cleaner shrimp in there about a week. Small guy. Will he pose a threat? I am thinking about trading him in for a peppermint shrimp if that's the case

 

[ss30]

I have had a cleaner shrimp in there about a week. Small guy. Will he pose a threat? I am thinking about trading him in for a peppermint shrimp if that's the case

TBH cleaner or peppermint wont make any difference IMO. Also both of them will move faster than the crab anyway.

 

[Sharkbait19]

Cleaners are harmless and too fast to be caught by an emerald.
Tbh a pep is a bigger risk due to chance of eating corals (so far so good with mine).