Help ID Parasitic Snail

[Brent F]

I noticed some smaller black bodied snails living on the back of a turbo snail. There might be another one on the inside (either that, or the bigger one bored through the shell of the turbo). What should I do about these?


Detail – Snail in red circle is living on the back of the turbo. Snail in red circle is living on back of the one in the red circle

Here’s a horrible picture of the black body of the snail