I wish we had access to seaweed but we're about as far from the sea as one can get in Scotland. I do use commercial seaweed meal though and sprinkle it along with other stuff on every bed before use.
We have sheep and poultry so no shortage of manure. Inside the tunnel I use well rotted farm yard stuff, plus the seaweed meal, chopped comfrey and for carrots etc which don't like manure I use garden compost made from garden waste without manure. For many plants such as tomatoes and squashes I dig a large hole and put plenty of that mix in, turn it into the bottom of the hole, then fill back in. That keeps the food near the roots and not so much at the surface where it isn't so needed.
I leave pea and been roots in the ground and let them rot down over the winter to release their nitrogen.
Outside in the main veg patch, for potatoes we rotavate in a lot of well rotted manure along a planting trench. To prepare a whole bed for the following year we spread fresher stuff, which hasn't had time to rot down, then cover it with a tarp and leave it for a year, by which time the soil is wonderful underneath, crumbly, fertile and weed free.
I occasionally sprinkle on calcified seaweed, as I don't use lime, but we are lucky to have a very well-balanced volcanic soil so it doesn't need much.
All this feeding makes the weeds grow really well