Shrimp Killer

[Aquattro]

I also just drop my shrimp in, no problems. I would suspect a mantis too, as they seem to be able to more easily get shrimp. Hermits are tough, I've never lost one to a mantis. I had a mantis banging on a snail the other day, no luck there for mantis either. Luckily I saw it and it was in a small isolated rock, which is now in quarantine in the backyard.
I've discovered new mantis and crabs in my tanks after years of running, so it is possible to have a long running tank and still miss stuff.
It could also be the 6 line, but you'd probably notice aggresion as soon as it saw the shrimp, not in the middle of the night.

[fishytime]

My sixline never bothered the cleaner shrimp that was in the tank before him, but went after a few other inverts that I introduced after he was in the tank. Never killed anything though(he's still just wee).

[Chowder]

Justinl I thought shrimp because that was the same way I found out I had one. I actually caught the third shrimp getting killed . That was when I realized it was a Mantis shrimp in my case. I also diidn't read that he had his tank running for a few years and yes he would have seen it if there was one. I would also lean towards the Acclimation if it is within hours that the shrimp are dieing but it sounds like he is taking every percaution there. I have a sixline that has taken out all my sexy shrimp.

[Seamonkey]

Well I'm sure there is no mantis shrimp in this tank. The new shrimp was small and no sign of a corpse. In the past the shrimp I added were in the tank for up to a couple of weeks. I figured the got attacked while they were molting and vulnerable. They were also larger. I'm very carefull to acclimate any new critters. The sixline wrasse just kind of has a predatory look to it and he's quite large. I suspect that he is the murderer! I guess as long as he's in the tank, shrimp are out of the question. (p.s. I'm a she not a he)