Technically, as far as I know, there are mainly three kinds: low temperature and high pressure grinding, normal temperature and high pressure grinding and chemical extraction. Low temperature, high pressure and normal temperature and high pressure are all physical crushing, which can retain almost all the active substances in them, and the color of natural seaweed remains emerald green. As far as I know, there are three or four kinds of plants that are emerald green. Chemical extraction mainly uses acid-base neutralization to extract acidic substances such as alginic acid, and many active substances in algae will be destroyed (most of the black algae in the market are produced by this method).
Algae content, some high, can reach 28%, some low, about 5% more, some just add without labeling the content. There are some pure hype concepts.
Finally, the effect of your own experiments is the truth.