I've had my 2" long tridacna squami for about a year now. I had him in my 90 gal community LR F and coral tank. This morning I woke up to see nothing more than one shell. Can't even find the other shell. Would either of these fish be the suspect: Niger Trigger (suspect no. 1), Yellow tang, Cole tang, Hippo Tang, Perc clown, YWG? I pissed to say the least! He was doing great. But after a year why now?