Marine macroalgae are considered to be alternative promising animal feed resources with numerous advantages, such as high growth rate, exceptional tolerance to be potentially cultivated in marine water and non-competition of arable lands for cultivation, over conventional terrestrial resources. Beyond that, macroalgae are rich exclusive sources of several bioactive components such as laminarin and fucoidan (complex carbohydrates), which are of growing interests for their potential beneficial impacts on health of livestock and fish. Dietary supplementation with algae and algae extracts was found to enhance the immune status and improve growth performance of fish. Positive improvements in productive parameters and general health have been observed due to the use of different macroalgae in fish diets. Also, macroalgae and their extracts are recently introduced as safer alternative prophylactic and therapeutic agents to control the infectious diseases affecting farmed fish. Several studies have shown that marine algae are a suggested source of antibacterial agents against both Gram-negative and Grampositive pathogenic bacteria. This review highlights the health benefits and the potential application of macroalgae phenolic molecules in fish nutrition. Moreover, this review offers future perspectives on curcumin and its nanoparticles, and their applications in fish nutrition.