Something eating away at rock??

[Les1]

In my one rock there are two little caves on the front of it. But in the one cave there is something black and shiny living in there, that comes out at night. I have never gotten a clear view of this creature, but I think from the looks of it that it might be a type of slug or something. But the thing is, I think it is eating away at the rock. Because the cave in which it inhabits has doubled in size in the last few months. And there appears to be waste at the mouth of the cave.
Have any of you ever heard of anything like this?

 

[Gary Majchrzak]

Time to haul out the flashlight at 1 am and meet the night shift! Probably an urchin!

 

[Les1]

Thanks for both your replies. I'll have to check it again tonight to see if I can see anythign more. As I said before there were 2 caves, but both of these caves are connected in the rock and sometimes I would see it move from one of the openings to the other. And when I looked at it yesterday it had filled in the one hole with rocks and shells. So I am thinking that it may be the same type of crab that you had in your tank jeff. By the way, this is fiji rock as well.
Thanks

 

[Tangy1]

Same exact situation happened a while back in a piece of my rock. It turned out to be a small 1/4" mantis shrimp. It would dig tunnels and deposit the diggings out of one opening. I noticed it because I kept seeing a dust storm emit from this hole. The mantis used to excavate all day long taking a break once in a while to poke his head out the entrance. At night it would close the hole using a piece of rock that perfectly sealed the opening. 9 months later the thing was about an inch long. If you watch the hole long enough I wouldn't be surprised if you see a couple of mantis eyes peering back at you.

 

[JKurtz]

Hi Less.
I had an identical experience with my Fiji live rock. About a year ago, I noticed one particular rock had a few holes in it, and occasionally some powdered rock would pour out of the holes. As it turns out, there was a crab in the rock, which, by the way, is still present in my tank.
It's very secretive and only occasionally dashes out from its cover to grab a food item. From what I've seen (which is very little) it's kind of a drab grayish black in color with very faint tan spots. Every once in a while, the crab blocks up its entry/exit holes with puka shells from my substrate. I assume it does this to protect itself when molting.
I haven't noticed it harming or molesting my corals or fish in any way--yet.
You might want to check the holes with a flashlight after lights out to see if you can spot anything crab-like in there.
Jeff

 

[JKurtz]

Oops! Sorry about misspelling your name, Les.

Jeff

 

[Les1]

Well, we found it, what ever it is. When I got home from work at the skatepark, my parents had the wonderful news that they found something new in the tank. It is a flat black disk shaped creature, kind of oval shaped, about one inch long and 3/4 and inch wide. It has a white spot in the center of it, and the bottom of it is white as well. Its sides look as if they are kind of frilly(sp?). They said that it was really stuck onto the rock when they tried to get it off, and they might have injured it while gettin it off...but it seamed to still be alive moving around in the container. I do not have any pictures now as it is late. But i have to get some up soon.

 

[Les1]

Well I found a picture of it online, I hope to be taking a picture of it today as well.
http://www.seaslugforum.net/scutus.htm

 

[Les1]

Well I don't know if it is this animal that has been eating at my rock. Because everything I read says that it eats algae. But there is definitely something...everyweek I see new holes in my rock. They are not little holes either, they're half an inch in diameter and go all the way through the rock. He is still alive in the container in my sump, and I would like to put him back in, but in the back of my mind there is something telling me not to, because he might be the one doing it. So I am not sure what to really do.

 

[Les1]

Well I got some pictures. They're not the greatest because I used my crapy computer camera, but there better than nothing. Its one side looks a little funny, but that just because there is some sand stuck to him.

http://www.angelfire.com/emo/crshoverr/Picture_17.jpg
http://www.angelfire.com/emo/crshoverr/Picture_22.jpg
http://www.angelfire.com/emo/crshoverr/Picture_23.jpg
http://www.angelfire.com/emo/crshoverr/Picture_24.jpg


I noticed that he does not like light to much. Because when I took a few pictures of him with my SLR camera he would shrink and move to get away from the light of the flash.

 

[Les1]

Lets try these...

 

[Les1]

Well angelfire sucks, I tried renaming the files to get them to show up. But its late, i'll see what I can do with them tommorow.