O.K. This thing will not come out on film so I am going to have to describe it and maybe someone has seen a picture or has some. I have three of these things crawling around my zooanthid covered rock in between the rows of polyps. They are not stinging them or the polyps are immune to them because they are not drawing up like when I had majano. This critter has the shape and look of a brownish green ricordia with small spikes coming out of its outter edge. I have actually watched this stuff move around the polyps and it moves pretty quick for an anemone. It doesn't seem to be hurting anything but before this thing poliferates I want to make sure that it is some thing I need to nuke. Sorry for no pictures and I will try and capture it on film and hopefully be able to post it. Thank you for any help I can get and if Jerel is out there this goes out to him as well. Thank you.
just from your description i would prolly guess it is somekind of nudibranch. i have not seen many turbo anemonea. also if you only see these guys in your zoo rock, that is another clue that makes me think nudi. i would also think that it could be eating your zoos. take a real close look at its path and look and see if you can see anything missing.
If this thing did not move and look perfectly round like a disc I would probably aggree with the nundibranch thing but it is as round as a quarter with spikes coming out of it's leading edge of the circumfrence of the disc. If you just look at it still you would think it was a small ricorda but it moves around. I am still trying to capture it on film without success. Thank you Doug for bumping it up. Hopefully someone has seen these things.
From your descprition I would have been inclined to agree with Geoff....the two spikes on the leading edge is what really pushes me that way....if it is hanging out in your zoo's don't take you eyes of that little sucker till you are sure its not feasting!