Just wanted to help clarify the third picture in my original post. That is not the astrea snail that you are looking at in the picture. That's the growth/snail like creature attached to the spiny star astrea and I'm zoomed in really close so you can see that whatever it is, it's extending that black tongue like appendage. A friend of mine suggested it could be a mollusk of some kind.
Here's a picture from further away so it's easier to see what I'm talking about...
Sent from my SM-N960W using Tapatalk