Urgent Shrimp & Crab Deaths

I have not been dosing them... doing nothing out of the ordinary, just seemed strange that the shrimps and crab were dead. I am wondering if it was not another fish or something, although I have not added anything in a good while.

 

no it was 2 dead shrimp. They have molted before, but this time they were definietly dead

 

What fish do you have ? Any hawkfish, dottybacks, wrasses......... Other big invert.

Silly I know but were the remains intact?

 

Yes the shrimp as well as the sally light foot were intact. I have a large blue tang, I'm thinking he may be the culprit although he has been in the tank for about 4 months

 

probably ammonia IMO. Also, is this going to be/is a reef tank? if so, raise the salinity to 1.025 but NOT in the tank if it has fish or inverts, but by water changes. Make sure your cycle is complete before being delicate fish or inverts, or else the money goes down the drain.