Mantis shrimp in there (or not?)

[fkshiu]

Here's the evidence:

The current tank (a 6' long 120 gallon) is now about 1 month old. All parameters have been consistent and are in good shape.

About half of the live rock came from my old 46 while the rest was cherry-picked from a number of reefers. In short, there's a wide variety in there. I "cooked" the new LR in the dark for about 6 weeks in hopes eliminating any ich and nuisance algae that may have tagged along.

I introduced an expanded clean-up crew about a week ago consisting of astreas/ceriths/nassarius snails and some scarlet hermits.

Yesterday I introduced a couple of blood shrimp, 2 porcelain crabs and a fighting conch. This morning everyone was doing well. One of the bloods had started exploring further down towards the middle of the tank while the other one stayed put in the same corner that I had originally introduced them.

I came back home this afternoon and found half of a blood shrimp carcass in the middle portion of the tank. It looked like it had been chopped in half. I could not locate its tail portion. The other blood was still in its corner.

About 6" away I find a hermit's body which looked like it had been ripped out of it's shell. It doesn't look like a molt.

Strangely, none of the nassarius snails were doing their usual "vulture duty" on the shrimp's body despite some juicy chunks of shrimp meat dangling out.

However, I have NOT heard any clicking noises, but it's a basement tank so I'm not always close to it.

Aside from the old clean-up crew, corals and a tuxedo urchin, the other residents are a regal blue tang, a royal gramma and two oc. clowns. They seem fine.

I set up a mantis trap by chopping the top off of a water bottle and inverting it back into the body of the bottle. I put some mysis inside for bait, but so far I've only managed to trap some nassarius snails.

Any thoughts???

[justinl]

I see no real evidence of a mantis. You heard no clicking which tells me that it probably wouldnt be the smashing kind of mantis. The other kind uses spears but is virtually impossible to get as a hitchiker. A smasher (more likely hitcher) will usually smash shells open, not pull hermits out. Spearers usually don't even bother with shelled things.

Have you tried staking out the tank? If you don't ever see anything unusual in the day, sit by the tank at night and watch and wait.

Did the old LR have anything in it that might have caused this kind of damage? Serpent stars? Big worms?

[RicePaddy]

On the odd evening I can hear clicking in my tank. But I have not been able to see anything. You mention that the Mantis would smash the shell to get at a snail or a crab. So I guess eveidence would be shells with holes in them?

Will

[justinl]

Do you ever get missing hermits/snails or their busted shells? If so then yes that would lean towards a mantis. A visual is of course the only solid evidence. Clicking alone is not hard evidence because more often than not, it ends up being a relatively harmless pistol shrimp. Or on the odd occasion a snail that is in front of a powerhead and is having its shell banged against the glass.

[RicePaddy]

I have found some shells with holes in the top and sides. Alot of holes.

Will

[justinl]

were the holes irregular like they were smashed in? or perfect circles. There are some snails that can grind through a shell to get to the insides. How often do you find these shells?

[RicePaddy]

I found two that I can see within the last two months. It almost looks like the shell may have degraded or I guess could have been punctured and peeled back. Hard to tell.

Will

[justinl]

I can't imagine a mantis of any species/size that could survive for a month between feedings. Do you have any other mysterious vanishings? If ynot, Then I doubt it's a mantis. And even if it is, a snail a month isn't such a bad price to avoid tearing down your entire system in search of something that might not even be there (that would be a let down and a half )