Who's the culprit?

Here's my current stocking list:

Coral Beauty
Blue/Green Chromis
Mated pair of Diamond Gobies
Hawaiian Feather Duster
Emerald Crab
Coral Banded Shrimp
and the usual clean-up crew....

First, I added a domino damsel (to my dismay, found it was a mean little thing). And he suddenly disappeared after having him for a week.
Tried again a few weeks later with a 6-line Wrasse.
He was there when the lights went off last night....and this morning he is no where to be found.

So....whoever is snatching my fish is obviously nocturnal.
My question is.....who is the culprit?
It's gotta be either the coral banded or emerald crab.....any ideas?
If that's the case, I want to remove him before my entire tank disappears over night.

Well, the first thing I thought when I found out he was missing was that he had jumped out. So, I searched all around the tank, filters, and the floor and underneath the stand....but nothing. I suspect that isn't the reason as I keep a tight lid on my tank.

I had a feeling that the coral banded was the culprit.....but can he really eat an entire 6-line overnight? Or is he stashing it away somewhere I can't find??

Nope - no clicking from the rockwork....

The weirdest thing is....this tank has had the aforementioned list of livestock for the longest time. This is the first attempt to add any livestock for about two months.
It seems as though the only fish that disappear are the ones that I add. I wonder if it's my tank's way of saying "no more".....