Currently, the search is on for alternative sources of feed ingredients, the main reasons being escalated cost and uncertainty of constant supply of common feed ingredients. The importance of algae as a potential substitute protein source for cultured fish feeding has been documented in recent years. Seaweeds are receiving consideration for their high protein value, essential amino acid content, vitamins and trace metals in fish feeding. As well as marine macro algae could be a potential low-cost source of protein for fish. Moreover, the economic comparison of feed cost indicated that increasing level of fresh and dried gut weed in alternative feeding treatments, commercial feed used for fish growth was reduced leading to significantly reduction of feed cost. Use macro algae (seaweed) in fish diets may improves growth parameters, feed efficiency, physiological activity, carcass quality, disease resistance and reduced stress response. This review describes effects of use macro algae (seaweed) in diets on growth performance of fish.