This Spanish fish farm is a major achievement! The importance of natural, controlled pond fertility as an alternative to manufactured fish food is can not be underestimated. It is an alternative to everything manufactured that is needed to build a food chain sufficient to feed populations entirely off the grid.
Here, waste from the river becomes purified. It is something of a manufactured delta that oxygenates the water through natural ebb and tide, removes toxins through plant and rock filtration, and bio converts to edible organisms as it reaches the ocean. Attracting birds from hundreds of miles as it springs to life with fish and the living algae, plants, decomposing organics, and small semi/aquatic organisms.
From this river it may be safe to eat the fish, though it may take some time to raise edible fish from the deltas of many of the worlds great rivers. Yet it is a great buffer, a green belt where ocean, inland rivers and land meet. As this practice expands far and wide we’ll be well on our way to recovering this planet from global warming.