crab?

what size is your tank, How many and what species of fish?
A chromis, gamma, flamehawk, and foxface any others?

Those 4 fish should do fine together provided you have plenty of nitchs to hide and your flamehawk is staying low. But without knowing tank size its all hypothetical.

 

72 bowfront
1 orange spotted gobby
1 percula
1 blue hippo
+ those above. plenty of hiding places

 

I wouldn't think any one fish is to blame for the death of your chromis. Could have just been bad luck.

The tank seems large enough based on your information but I wouldn't add anything else fish wise. with exception of 1 to 3 more chromis since they like to always be out for your guest.

I have read in the past there are 2 species of chromis being sold in many LFS together without distinction. One has a faint black dot on the tail the other does not. They do not get along together.

 

these two were tank bred together. I'm not adding any fish until some die or I kill another one if it stings me again. hint hint.