You are getting sheets of high quality "Nori" seaweed. The nutritional value of nori, being high in carbohydrates, protein, vitamins, and especially minerals, they began using it to feed their saltwater herbivores.
It is ideal for feeding tangs and surgeonfishes, some angelfish and blenny species, as well as many other types of algae eaters like hermit crabs and snails.
Nori seaweed draws an extraordinary wealth of mineral elements from the sea that can account for up to 36% of its dry mass.
These nutrients include sodium, magnesium, potassium, iodine, zinc, Beta carotene, vitamin A, vitamin B complex, vitamin C, and calcium.
It is important to NOT overfeed, as any excess Nori that is uneaten may contribute to the lessening of the water quality in the aquarium.
Only feed what the tank inhabitants will consume in a short period of time, removing any excess nori that may be floating around in the water or that settles on the bottom of the tank uneaten after an hour or so.
To enhance its nutritional value, you can option to apply a few drops of a liquid vitamin supplement such as Selcon onto the dried Nori and allow it to soak in before feeding.