By mistake, I used the seasoned Nori for about 6 months before switching to unseasoned Nori. The seasoning ingredients are sesame oil and soy sauce. I am not sure what affects sesame oil or soy sauce have on marine livestock. All my livestock seemed to be doing fine.
Now I use unseasoned Nori. Everyone (Tangs, Chromis, Clown, Goby) in my tank loves Nori.
I've also found fresh (not dried) Nori packaged in salt kept in the fridge section. Anyone use that?