Wow, now I also believe that I don't feed enough nori!
I have a foxface, scopus tang, naso tang, pyroferus tang, and lieutenant tang (other fish eat the nori too). I feed about 1/2 sheet, folded and stripped in a clip but only about every other day or less. I mainly feed LRS herbivore frenzy which has quite a lot of veggie matter in it. I also throw in rocks that are covered in turf algae (from the refugium) and this is a nice treat for them to graze over the course of a day or so (depending).
Normally the nori gets consumed within minutes. Because the naso and the pyroferus seem to prefer the nori more than most other foods, I think I will increase the amount I feed. None of the tangs are skinny (the Lt is super fat!), but the pyroferus and naso could put on some weight. Decision made. Glad I found this thread.