I just bought a clam from my lfs, but I noticed that in the bag there are these little things that look like feather dusters but some of them are swimming around in the bag. I cant take a picture right now. Any ideas on what they could be?

maybe hydroids? or any other ideas?

is there a way to dip the clam?

That's a bit too vague without pictures... You can dip a clam, but I wouldn't. Are you sure they're not pods, mysid shrimp, or something along those lines? Hydroids are quite tiny, even when they're freeswimming.

^ this.

Have you done a freshwater dip? Do you have a way to QT them?