you mean like kelp? I know it is used in japanese sushi for wrapping the fish, right? It is supposed to be very high in nutrients. Can't help you much. sorry

Kelp has many trace nutrients and mineral in it. It is good for you but you don't necessarily have to have kelp supplements.

Protein balance is probably the one thing you need to be aware of. Soy products will provide protein. Are you vegan or lacto vegetarian or lacto ovo vegetarian? If you still incorporate dairy products you can pair up a dairy item with a whole grain item and get a full complement of protein. Eating eggs (ovo vegetarian) will give a full protein. Whatever diet style you follow is fine. Just be sure your protein is adequate.

Eating a vegetarian diet should provide the nutrients you need. I am not sure why you were told to get a supplement for sea weed. It won't hurt but I am not sure it is necessary.

Would seaweed may be have the extra iron that is sometimes missed in vegan diets? I remember a long time ago, vegetarians were becoming anemic because they never got enough iron which is usually found in red meat (like liver) or in spinach. My son loves spinach but we don't buy it often.

Yes that may be a part of why they recommended the seaweed. Anemia comes in several forms. There is pernicious anemia which is a lack of B12 which is high in red meat. You will not get this in any plant material. You will need to take a supplement for this. It is important to do so. Being vegetarian takes some knowledge and responsibility. It is important to make sure you replace nutrients that would have been intrinsic to meat or poultry. It is not hard. Google the subject. You will get more hits than you know what to do with. Start slow and build.

Feel free to ask questions. I will try to help. I have some knowledge but I am sure I need to learn much more.