Translucent Green Spiral "Shell" on Coral

[Morphix]

This Candy Cane is dying (I can't keep them alive for some reason) and I was pulling it out, I found this thing on the back of the coral. It's affixed firmly, and seems to be some sort of shell. It appears dark green under lighting, and has an opening. By the texture of it it seems to be Calciferous and if I pry at the opening i can damage it. The "shell" is translucent but I can't actively see anything inside it. Definitely was not there when I added this coral a couple months ago, coral was dipped before adding to DT.

 

[duberii]

Looks like a huge vermatid snail- the mucus that they use to catch food in the water is really irritating to corals and could definitely play a role in your candy cane receding. Glue the opening and it'll starve out the snail.

 

[Morphix]

If it's a vermatid snail it's the biggest one i've ever seen.

 

[duberii]

Yeah it looks like it- I've never seen one that big either but I guess if they are getting enough nutrition they can grow pretty large

 

[king aiptasia]

some species of the genus Vermetus can be over 5 mm in diameter