There's a lower-tech way to get algae on board - feed them the micronutrients they're limited by in the ocean, which is mostly iron: https://en.wikipedia.org/w

There's a lower-tech way to get algae on board - feed them the micronutrients they're limited by in the ocean, which is mostly iron: https://en.wikipedia.org/wiki/Ocean_fertilization https://en.wikipedia.org/wiki/Ocean_fertilization https://en.wikipedia.org/wiki/Iron_fertilization https://en.wikipedia.org/wiki/Iron_fertilization