A nocturnal anemone

[Jaybird]

I initiall thought these things were aiptasia but am not so sure anymore. They don't look like the typical aptasia and as the lights on in the tank come on....they tuck themselves back into the rock until it's dark again.

They do pull themselves back into the rock if you go near them...similar to aiptasia....but don't come out at all if there is a lot of light. I've never heard of a nocturnal aiptasia.

The picture is pretty much crap, but these guys are small. The largest is about half as large across as a pencil eraser. You can't see from the pic, but the grey point you can see in the picture form what looks like a pentagon from above. They are so small that the refraction from the glass at another angle distorts them so much that the pictures are just a blur. Again, to give a size reference....the small white bits you see around it are my substrate sand....sugar size.

 

[Kurt_Nelson]

They look a lot like a type of anemone I have in my sand - there are actually "sand dwelling anemones", and they're nasty. I can't keep the small nassarius in my tank anymore because these things devour them. I'll see if I can dig up my post on them.

I haven't found a good way to control them yet. A shot of kalk paste in their mouth seems to work, but I just have too many of them for it to be effective.

{edit: found the other thread... http://www.aquariumadvice.com/forums/f18/strange-beasts-in-my-sand-111342.html }

 

[roka64]

Kurt, try mixing the kalk with a little more water. That will help it cover more area.....

 

[Jaybird]

I took the rock out and used a little reef epoxy over two of them. With the lights on they have pulled themselves right into the rocks, so it was easy to push a small piece of putty over top of them. They won't be seen again....except for that third one I couldn't see. they are small