When you buy the nori, just make sure it's not seasoned -- some are seasoned with soy sauce or other ingredients, so just check the list of ingredients (unless you think your tangs will like soy sauce
) Also, if you can find an Asian market in your area, they are usually a lot cheaper than the supermarkets.
i feed my tangs: mysis shrimp, frozen brine, formula #1, formula #2 and the algae sheets. they will eat just about anything and i think the variety helps them look their best!
Many tangs are actually omnivore, yellow is one of them. You should feed your yellow mixed food type but kept plant based food as dominant source of nutrition.