Edible seaweed

Are you looking for regular seaweed?

Edible seaweed is a type of food that heals 4 hits. It is uncommonly used or traded since it may only be obtained after a successful catch for the Fishing Trawler minigame. Acquiring the seaweed provides the player with 5 fishing experience.

As the name suggests, it can only be eaten and does not serve in the making of soda ash.