Unexplained deaths...

[DLHDesign]

I came home to find that one of my fishes dead. No obvious reason I could find - the only slight clue was that both crabs were on top of it. I suspect that's a "food available" thing more than the perpetrators...
Strange thing is; this happened the other day as well. This time it was my coral beauty; last time it was an anthias. All fish and corals in the tank were fully QT'ed, all eating well, no excessive bullying that I've observed. Nothing about the tank hast changed in months. I just did a water change a few days ago, but nothing about that was uncommon.

I didn't have time to diagnose the last fish, but this one I put into a FW dip (black-background pics):

Anybody see anything? All other fish in the DT are doing fine; no abnormal behavior at all. Could it really be that the crabs somehow caught two fish? :-?

 

[Humblefish]

What kind of crabs? Large or small?

 

[melypr1985]

In the very first picture it looks like there are some missing or damaged scales. Are you sure there aren't any predatory crabs or other hitchhiker in your tank?

 

[DLHDesign]

Two hermits in the tank. First one is in a shell that is about 2" in length. Second is closer to 1.5" shell. They've both been in there for some time, but have (at some point since initial introduction) swapped into a new shell. So - growing, I guess?
They are both Halloweens, so... perhaps it's them? :-\

(Fun fact: The frag plug in the second picture was "firmly" pushed into a rock hole (but not glued) a few minutes ago...

 

[DLHDesign]

Are you sure there aren't any predatory crabs or other hitchhiker in your tank?

The two above seem likely culprits...
To be fair; I'm not sure how long the fish was dead for. I can't specifically recall seeing it feed this morning, but I was having a crazy day and didn't look for it either. I found it in the front-corner of the tank when I got home. Could be (in other words) that the scales came off after the death. Perhaps....

 

[Humblefish]

@DLHDesign Most crabs become predatory as they grow, oftentimes ambushing fish as they sleep. It’s just in their nature. Personally, I’d get rid of them or sump them.

 

[DLHDesign]

Totally gonna happen; cheers!

 

[4FordFamily]

Those look like very small crabs... I’d be surprised if they killed a CB angel, but I could be wrong. I have a giant crab the size of my thumb in my tank and I’ve had him for about a decade and I’ve never seen him eat any fish, or had any strange disappearances but I don’t know what type of crab nor do I know my crabs well, in fairness.