I have had this clam for almost a year, very healtly and responsive. But, I'm worried about a mat of what looks like star polyps that is growing outside the shell. Will it kill it? Will it stop when it gets to the edge of the shell? The clam is attached to a rock and the polyps own that rock. What should I do?

Should be OK. I have seen a picture of a local Texas reef keeper that has the same thing going on with his clam. The clam is not worse for the wear.

Thank you.. anyone else has heard or dealt with this?

my LFS has a clam that in over a foot big, it has yellow star polyps, xenia etc... growing on it looks really awesome

Well.. lets see how it turns out.

um id be carful with green star polyp. some things can grow and be fine on the shell like yellow polyps and stuff, however creeping growers can sometimes grow on or under the clams mantel. causing a hole... then death.

just be careful, personally i wouldn't want that on my clam.

You can use kalk to kill the edge of the mat of the offending star polyp and keep it from spreading to the clam.