Seaweed has 60 nutrients in it that benefit the garden. It can act as a fertilizer and increse soil structure or be a mulch to keep down weeds. It is the BEST singular thing for a garden. No other additives or ingredients needed.

i think for Chapter 3, it should be used in creating better soils. Maybe as an ingredient for increasing soil tiers. Not my place to tell you what to do, i'm just letting you know that seaweed is awesome for the garden. Take it from there.