something killed my new royal tang

[rags111875]

i've had a 2" royal tang for only 4 days and found him no longer swimming in my tank. looked everywhere and finally saw a group of snails doing their job. the tang was between my candelabra and a piece of rock (dont dead fish float?). perhaps a mantis got him (i've been hearing some clicking lately...TBS rock...already took out 6 from the beginning, but havent seen any since the last one i took out a month ago). i also know that i have a big pistol nearby. when i scooped up the carcass, it was missing eyes and its yellow tail. there was also a gorilla crab (about the size of a dime) feeding off the body. water params are perfect. only thing that changed was a 4 degree drop in water overnight (went from 82-78degrees due to my a/c finally deciding to work for the day). any ideas?

[Rendos]

A mantis could have done it, but there is always the possibility that it just died and the cleanup crew (snails/crabs) were just doing their job. The first thing they usually eat are the eyes, and fins.

[rags111875]

got a couple questions:
1. do dead fish float?
2. how likely is it that gorilla crab killed the fish?

[Frick-n-Frags]

I would guess it probably died on its own. The scavengers are going to ravage the remains, but that doesn't mean they jumped it.