Fucus vesiculosus, known by the common names bladder wrack, black tang, rockweed is a seaweed found on the coasts of the North Sea, the western Baltic Sea and the Atlantic and Pacific Oceans. It was the original source of iodine, discovered in 1811.

The fronds of Fucus Vesiculosus grow to 150 cm long and 2.5 cm wide and have a prominent midrib throughout.

Fucus vesiculosus contains varying amounts of iodine. Iodine might help prevent or treat some thyroid disorders, obesity, aging skin and constipation. 

Also might have antidiabetic effects and affect hormone levels.

Making tea: Add 1 teaspoon of dried bladderwrack to a boiling cup of water and allow it to simmer for 10–15 minutes.Three cups per day of tea can be drunk. No more than 150 mcg iodine should be consumed from all sources, including bladderwrack, per day.