Have a feeling its not a bad one.....but unsure. He came into the store in the same bag as a fish, and is surviving in a fish only tank very well, and has been in there a while. He has found something to live on, but dont know what yet.
Wow really cool nudi! I always check out the seaslug site when I want info on nudis. Here's the link for this one: The Sea Slug Forum - Phyllidiella pustulosa check out the postings at the bottom too for more info.
Everything I can find point toward it being a sponge eater.