Mysterious predator, pretty worried.

If you have a bobbit worm I'll buy it off you. But it sounds like a mantis, ill also buy that from you.
-Chance

 

Here's what you should do, take a bamboo skewer, and put something tastey on it (shrimp?). Wave it.around in the tank and see if the predator comes out.

 

I used to pet mine. All my fingers are intact!

 

I'm going to have to disagree with a mantis shrimp. I've never seen smashers hide in sand and drag prey around above the sand. Plus, you'd have heard it if it was a smasher. Can't be a spearer because they go for soft bodied animals (fish).

While mantis are fast, you'd definitely see it if it was going after prey. Mine was very inquisitive and would rotate the hermit crab around, looking for a perfect hit spot.

Could be a bobbit worm, or maybe even a brittle star (reaching out on a limb, no pun intended).

 

I don't think Bobbit worms are very common in aquariums. Even as a hitch hiker.

Where did you get your LR, and sand?

 

The method of capture does not sound like that of a mantis. It indeed sounds like a worm with it coming up from the sand like that. I've also seen bristleworms try to pull large food items into a small crevice.... all the while never seeing the worm until I removed the food item (usually a recently deceased friend). I can picture exactly what you are speaking of..... but as you know, bristeworms will not attack healthy specimen, but a Eunicid sure would.

Here's my Eunicid all kinds of ticked off when I was trying to photograph him.

 

No but you hear about it because they are very lethal. I'm reading a tread like this on two other forums right now.

 

Oh and the slimy ball of sand you were describing.... that's the Eunicid's front door you were messing with.

 

Well I watched it take out a snail last night. Shell is about 1" across and he had no trouble moving it back to his cave on the bottom of the live rock.

After doing a bunch of reading I'm fairly certain its a oenone worm. They are aggressive, and prey mainly on crabs, snails, clams. The slime trail is very characteristic of them, its a toxin that is believed to both paralyze and begin digesting the prey.

I watched it for over 1/2 hour. It always leaves the tail rooted into the live rock, that combined with its slimy tunnel enable the lightning quick retreats. It was stretched out about 6" beyond the rock, probably more considering the way it was wrapping itself around the snail shell, and going inside it to attack.

Wow, crazy creature. I might try and capture it -not easy to do, so I'll probably pull the rock and try to coax it out.

Any experience with the dreaded OENONE WORM?

 

Sounds like a spoon worm, from hell. I've had no experience with said worm. My only words to you, are good luck!