I've been taking algae supplements lately. It tastes like fish food because it is fish food.

Apparently, it was a source of cheap protein during wars, but didn't provide enough nutrients and tastes like pond scum. It ended up in the supplement sector because it was easier to get approved as it over food. Soylent Green was inspired by it.

I hope it does go back into the fish food sector - it's cheap and nutritious but tastes worse than soy.