ID tiny tube on my clam?

[tebstan]

I got a little clam, and was inspecting it pretty closely. There's a bunch of little coiled white tubes that appear to be empty. But there's also a tiny red tube that isn't coiled, and is occupied by something. I can't get good pics.. I can barely see it, and using a magnifying glass hasn't helped me feel comfortable with an ID. 'Something' retracts into the tube occasionally. Could be a tiny duster or vermetid snail? Is there any way to differentiate on something this little? I don't want vermetids to spread, but I do want dusters to spread.
The clam is unaffected. It appears to be healthy and showing growth.

[txav8r]

Try looking here:
http://www.maast.org/forums/showthread.php?t=52760