Slugs with green spikes???

[nikki_pip]

Hi
I have a few slugs in the tank which have bright green spikes any idea what thy are called? Will attach a photo but not a very good one
Thanks

 

[nikki_pip]

Photos

 

[melosu58]

Need a better pic to be sure but I believe him to be a nudiebranch. Here is an example of one. See if you can get a pic from the top.

Saltwater Aquarium Sea Slugs for Marine Reef Aquariums: Lettuce Sea Slug, Green