There's a sea monster in my rock

[Leetch]

Ok, so the other day I saw a crab shell sitting in one of the holes my blenny likes to go into. I left it alone thinking it was a crab that found himself a gold mine. A few days later the shell hadn't moved so I figured he ate himself to death and all that was left was his poor little shell so I tried to remove it. Being the hole was so small (approx 1/2"), I succeeded in only cramming the shell farther into the hole. An hour later it was back a the top of the hole again. Being the unrelenting male that I am, I tried again.....and again...and again, time after time for about two days, each time pushing the shell in, only to find it pop back up again an hour later.

After a few days I realized I was either on the fish version of "Punked" or there was something fishy in my rock. I decided to open the hole a little wider so I could remove the shell and let my little blenny regain his home. I was able to finally remove the shell when all of a sudden I see a pair of eyes peering out at me from the shadows of the hole. It would not come out far enough for me to i.d. it but it's eyes were definately crab looking....but again no other defining characteristics. Unfortunately in the meantime, one of my blue legged crabs decided the shell I removed was a more suitbale R.V. than the one he had so he changed shells. I put my blue legged's old shell on top of the hole and the creature from the black lagoon took to it right away.

Now, I have only ever purchased blue legged crabs and scarlet hermits who are very mobile and not akin to living in a hole. This leads me to believe that somehow I've secured a hitchiker, which I believe to possibly be an emerald crab, although I can't truly i.d. it without being able to see anything on it.

Does anyone have any ideas what else it could possibly be? It's strange because this live rock has been in there for at least 6 months and this is the first time I've seen a bug eyed creature staring at me from the abyss.

[Original Fin]

I have a similar story, and I've been able to identify mine as some sort of Xanthid crab. Red Eyes, hairy legs, black tips on claws. I haven't lost any fish, but early on there were some mysterious snail and small hermit dissapearances. Nothing lately though. I see him hanging out quite a bit next to my BTA. I think he's after the remains of silversides I've been feeding the nem. Doesn't seem to harm the nem in any way, but I know there are ways of trapping them if it becomes a problem.

[Original Fin]

Found this on the sand bed a few weeks ago...same type, just a little smaller.

[Sabre]

Mantis shrimp have been know to hich hike also. if so feed him alot get him comfortable with your aquarium and then grab him and get him out. (with a grabber)

[Leetch]

Well I still haven't been able to id. Good thoughts on what it might be though. Whatever it is has recently completely closed up the hold on the front of the rock. It used the shell to cover part of the hole and some other stuff to completely close it up...I'm assuming it used substrate or loose rock.

I've watched very closely at night but still haven't seen anything. I'm assuming it has an exit hole somewhere in the back or bottom of the rock where it comes out and feeds but it still evades being identified.

I did have a fish disappear a few months ago, but I assumed it just croaked in the rocks and the crabs finished it off. I have noticed a few weird things on my sand lately though that I'm not sure if it's weird shaped rock or old fish bones...lol. I'll have to pull it out and see

[Leetch]

Mantis shrimp have been know to hich hike also. if so feed him alot get him comfortable with your aquarium and then grab him and get him out. (with a grabber)

I think you're right on the mantis. I've been watching him over the last few days and he keeps peeking out, especially at feeding time. I noticed the stuff he uses to open and close the whole looks a lot like crushed rock and that mysteriously I have a few chunks of rock that have fallen off in the back of the tank.

This leads me to believe it's the smasher type. So far I haven't had any lost fish but a snail or two seems to be missing. He looks fairly sizable (based on his eyes and how far they stick out) so I'm getting a bit worried that he might get a little too hungry and try to catch one of my fishies.

I'm going to call my LFS today to see if they want him then do my best to catch him without getting a finger smashed. I think I'll try to remove the rock and blast some freshwater at him to see if he will run out then snatch the rock away from him. Wish me luck.

[Chasman]

Leetch

I had one in my tank at the initial set-up from the live rock. I bought an X-Terminator shrimp trap and it worked. I got it on the internet for around $13. Google it and you will find them. There are some DIY traps that work too. I made one for a crab I had. Caught him pretty quick.

Chasman