Reducing the environmental footprint of aquaculture has become a high priority as part of the drive for greater sustainability in modern society. To date, a major concern has been the challenge of feeding farmed fish with products that are nutritious but, at the same time, economically and environmentally sustainable. This guide sheds sheds light on the different sources of feed ingredients provided to fish during their life cycle. It should prove to be a very useful tool for anyone – researchers, professionals, and governments alike – who aims to reduce the impact of the aquaculture industry on marine and freshwater resources.