haha i just got one too, now you got me worried. i cant keep the guy in one area. he keeps moving and unbarrying himself, its pretty annoying.. any suggestions

I just picked up two of them as well , mine are staying where I put them. Maybe you have them in an area with too much flow? Mine are off in the back corner in a lower flow area.

What kind of substrate do you have? How deep is it? Cerianthids like to bury themselves in several inches of sand at least. One thing I've heard of is placing them in a wide diameter PVC pipe section and filling it with sand. It may also be flow related, as wheelman suggested. Nothing too strong/direct from what I've seen.

Be careful with these anemones. They will grab anything they can and pull into their mouth :P

Lighting is also an issue to check out, they are not find of too much light.

Thats why I will try and keep him small. I have him in the front of my tank where not to many of my fish swim