Picky eater

[DSlater]

Agree with the above posters. The fact that your Naso is picking off your rocks is a good sign.
Our Blond doesn't like the purple or red, Julian Sprung seaweed. Loves the green sushi nori that we get from the grocery store and mixed with garlic.
In general, the Naso is a laid back tang. Took ours close to a month to start eating heavy, now goes through a full sheet a day along with a meaty meal.
With other tangs we had to grind shrimp into rubble rock to teach them to eat. Knowing where the food comes from is part of the battle.