Fish farming often employs high stocking density (HSD) to boost productivity, despite the fact that it leads to chronic stress in fish, resulting in impaired growth, reduced reproductive capacity, and increased susceptibility to diseases. To mitigate these negative effects, incorporating appropriate levels of essential polyunsaturated fatty acids (PUFAs) into fish diets has shown promise in modulating stress responses and promoting the production of healthy fish for human consumption. The Amaranthus plant represents a valuable source of essential fatty acids (EFAs) and long-chain PUFAs, along with other essential nutrients. Almost every part of the Amaranthus plant can be processed and readily included in fish diets. This mini-review aims to provide a comprehensive understanding of the synergistic effects of Amaranthus-enriched fish feed on growth performance and the tissue profile of omega-3 and omega-6 long-chain PUFAs in cultured fish.