I lost two of my firefish in the past 3 days. The tank is 180gallon and I don't see any suspicious activities. i do have a flame angel, a purple tang, a sailfin tang and a percula clown. I have a pistol shrimp (could he be the assailant?). I have seen a crab in the tank (not sure what it is.. gorrilla?). i can't see any trace of the fish Thoughts?