Are Coral Banded Shrimp/ Large Emerald crabs fish killers??

Crabs are opportunistic feeders. I wouldn't put it past a CBS either.No way you can tell for sure. They are both unknowns. You could remove those unknowns to the sump, which would help you narrow down the problem.

 

How long has this tank been set up Kirk?

 

Do you feel the tank has fully cycled? I know you know what your doing----but I remember loosing fish left and right for about the first 5 to 6 mos. of the set up, I just assumed I didn't let the tank fully cycle, all has been well ever sense then, I wouldn't think the emeralds would be killing fish, and I have read some horror stories on the CBS.
Is it possible for you to take Tibbs' idea and run with it?

Good luck, John

 

Where is the rock from? Sounds like you have a predator on your hands. Could be anything from a mantis shrimp to octopus.

 

I had the same prob... I bought so live rock at a lfs and I had a tag along with the rock.... A mantis shrimp hiding in one of the holes in the rock....

 

Do you still have the mantis? I have been looking for one for some time.

 

I've never witnessed it myself directly except I have seen them behave somewhat peculiarly. In any case they are often implicated in these types of crimes, but that's all somewhat hearsay from customers over the years

 

I have a large CBS and a couple of smaller fish in the tank. If my CBS was going to kill something, he probably would have gotten the small green mandarin a long time ago.

--AJ