View Full Version : Mysterious Snail-thing

09-26-2008, 01:13 AM
I first noticed this 'thing' in my tank back in 2006. The first time it caught my attention was when I noticed it on my zoanthid rock. Thinking it was a discarded (or even occupied) hermit crab in a snail shell, I tried to brush it off the zoanthid rock. But it didn't budge. It was firmly attached to the rock. I figured maybe the hermit crab abandoned the shell or maybe even died and the surrounding zoanthids began to encrust it, and basically cemented it in place (that was what I initially thought).

For a solid YEAR, this thing appeared to be just an empty shell that had become firmly attached to the rock by enrusting zoanthids. Every now and then I would try to pry it off, but it would not budge, so I just left it. After all I've got empty snails shells here and there in my tank (from hitch-hikers, not from anything I've purchased).

Then one day I noticed its position changed. It began to detach and move. It took some force to pry it off, and when I did, I was suprised. This thing was ALIVE! Some sort of snail or snail-like creature (whelk, etch) which was capable of being TOTALLY IMMOBILE for a year.

I was mistaken that zoanthids had encrusted it, they had merely grew around it, with much of the polyps obscuring it. I remember moving it about 1ft way on another rock. And to my complete surprise the next morning it had mysteriously returned to the EXACT same spot it had been cemented to for a year. Figuring it hadn't done any harm to the zoanthids or anything else in the tank, I let it be. It returned to complete immobile dormancy....another year passes.

Then today I found it on the glass near the top of the tank. I temporarily removed it from the tank and took a photo of it:

I then returned it to the tank, on the glass, in the upper right corner of the tank.


For the two years it's been in my tank there's only between 2 days when it was NOT attached to a particular zoanthid rock and at a particular SPOT on that rock. When on the rock it has been completely motionless. Excluding 2 days in 2 years, it doesn't move at all. I'm not sure what it eats or consumes, but it's not an algae eater (which are usually roaming and are attracted to areas where algae is) or a detrivore (I had a carnivorous whelk in my tank which was a fast mover, and attracted to food...this particular snail or snail-like creature never moves, except for one day a year as the current trend goes.

I placed it in the front upper corner of the tank. It will be interesting to see where it will be tommorrow. I will be completely amazed if it again returns to the spot it usually 'cemented' to.

Any idea what this is?

09-26-2008, 04:19 AM
from the 2nd pic it looks like a snail to me, but its amazing how it made it all that time without food

09-26-2008, 05:10 AM
Maybe it moved at night and Just went back to the same spot before you got up?

09-27-2008, 12:16 PM
I forgot how to distiniquish snails from whelks (I think the shells spiral in opposite directions), or if there are other snail-like creatures. But it's definately not an algae-grazer. It lacks the mouth or rasping tongue that those typically have, or at least hasn't revealed it.

Except for the two times mentioned it's been completely stationary, in a spot among the zoanthids. I have no idea what sustains it or what prompted it to suddenly up and move after not moving for such a long period of apparant dormanancy. I view my tank very often at night, and even in the late hours of the night on the weekend, and it just doesn't move.

Since starting this thread, the snail has anchored itself at the very top of the front tank glass very close to the water line (so I can only see it if I view the tank for the side). I'm thinking of putting it back down on a clear section of rock.

Very odd creature.

09-27-2008, 04:17 PM
I have a snail like that, that only sits at the polyp base of my frogspawn. It NEVER moves. I took it out to look at it and but it back and it made it to the frogspawn and hasn't moved since. I'm still digging to figure it out. I'll get back to you if I can ID it.

10-23-2008, 03:06 AM
For about a day or two after my last post, this snail took to hanging out on one of my powerheads, even when I placed it far away among the rocks, it still homed-in on that particular powerhead (would be back on it by morning). Then it disappeared.....for a few weeks.

I noticed it today, anchored in the middle of a field of zoanthids (it seems to like being surrounded by zoanthids, for some reason).

If it behave's as before, it will likely remain planted where it is (indicated by the red arrow) for a good year or more:

Interestingly, this thing has outlived all of my original store-bought snails.

10-23-2008, 03:15 AM
Sounds like it likes that spot but does move around and eat at night.

Have any moonlights?

12-14-2010, 12:36 AM
2010 update:

It's been over 2 years since I've last saw this thing, but this creature made another rare appearance.

Saw it crawling across the front-top part of the tank last week, and it's disappeared again. The way things are going I'll probably see it again in 2012.

It's been in the tank since I set it up in 2006.