Since I am not going to eat snails or calamari I'll stick with blue green algae which is what fish eat that gives them the DHA in their tissue. Big plus is its ecologically sustainable.
Algae, one of the most abundant organisms in the ocean, are marine-based photosynthesizing organisms. That is, they live in water and make energy from sunlight. They are simple one-celled organisms that contain three components that make them nourishing to eat:
Chlorophyll and other plant pigments Omega-3 fatty acids as EPA and DHA Marine minerals such as iodine