Help please snail shell growth!

[ReefKnot]

I've actually posted about this before but no one seems to be able to help identify it for me. There is a growth on one of my snail shells that has doubled in size since I got it a month ago. It seems to look like a blister, and there is a hole that seems to be able to open and close. I am unable to determine if there is anything inside this growth. I have one pic currently, but I am going to try to get another one now. The growth is slightly larger than it was for this picture.

http://s1092.photobucket.com/albums/i411/Michael_Wrenshall/?action=view&current=IMG_0836.jpg

 

[Reefphile]

It/they are likely barbacles. Google barnacles and read up on them.

 

[ReefKnot]

Awesome, that is totally what it is! Thanks! This is my first saltwater tank, and seeing that white thing get bigger and open and shut, I had no idea what it was. Is it dangerous in anyway to the tank, or just a harmless filter feeder?

 

[Elysia]

As long as the snail can keep moving, the barnacle is harmless, and will likely die when it can no longer capture enough food to maintain its bodyweight. It can be difficult to keep filterfeeders alive.

 

[ReefKnot]

I have spotted a couple others on other snails, which did not have them before, is that normal?