I’ve recently started pulling aquatic (freshwater) vegetation out of my friends pond for mulch. I’m sure it’s not as nutrient dense as seaweed, but it works really good. No weed seed spread with it and it’s insanely prolific
Discussion
Seaweed is good it's has a lot of micronutrients and growth regulating things like auxins in them.
If what your putting on works that's great. Might be worth seeing if you can pair it with some biology to see if you can make it even better though.
Quite a few people permaculture related people are working on a plant nutrient database. So in the near future we should have a better idea of what we are dealing with for all plants.