hitchhikerid

Lately one of our corals has been staying closed and we weren't sure why but with it being closed, today I noticed a feather duster and this thing that kind of looks like a feather duster but is different from any feather duster I have seen! It reacts to movement just like a feather duster...

Just noticed some little additions that I hadn’t seen before. Does anyone know what my little hitchhikers are and if they are dangerous? Thought maybe Asterina, not sure what the others are near my mushrooms thanks in advance for any help!

I see these stringy things coming out of the sand all the time. I believe the worm stays under the sand and puts the strings out. I saw it on the glass and tried to take some pictures. Let me know if you can identify this. Thanks

Hey guys! Any ideas what this could be attached to my little snail? Good guy? Bad guy? How to remove if bad? Thanks! Tank contains: 5 snails, 2 occy clowns and a blenny