Nudibranch ID please

[csreefs]

I found this little guy on my Bam Bam zoas this morning. He seemed to be irritating them. As you can see, he lost a few tentacles (?) when I suctioned him off the frag.
My best guess is a Spanish Shawl or an opalescent nudibranch?

 

[ISpeakForTheSeas]

I found this little guy on my Bam Bam zoas this morning. He seemed to be irritating them. As you can see, he lost a few tentacles (?) when I suctioned him off the frag.
My best guess is a Spanish Shawl or an opalescent nudibranch?

You'll need some closer pics under white light for an ID - straight-on pics of the top and side showing the slug's full length are good; for species like this, a close up of the "tentacles" is also helpful.

Edit: Just to add the "tentacles" (a good description for them) are called cerata (or ceras, for the singular noun).