Generally, fishes are continuously exposed to several aquatic pollutants originating from agricultural runoff, mining activities, discharges from industrialized regions, or other sources that throw their polluted water into the aquatic ecosystems. Fish exposure to pollutants such as heavy metals, pesticides, herbicides, and other toxic chemicals will negatively affect their health and welfare. These pollutants may induce growth retardation, oxidative stress, genotoxicity, reproductive disturbances, haemato-biochemical alterations, immune suppression, increased susceptibility to diseases, high mortality rates, and great economic losses. Therefore, researchers have paid utmost interest in finding functional feed ingredients to maintain fish health, increase productivity, and improve the aquaculture industry. Microalgae have gained great importance as a promising and functional feed ingredient because of their high nutritional values. Moreover, their bioactive phytochemicals also possess important functions, such as anti-inflammatory, antioxidant, immunomodulatory properties and several others. In this concern, many studies highlighted the health benefits of microalgae for farmed fish, such as improving hepato-renal functions, immunity, and antioxidant capacity. This review article provides a new approach that discusses and evaluates the potential efficacy of the cyanobacterium Spirulina (Arthrospira platensis) and six microalgal species, namely Chlorella vulgaris, Chlorella pyrenoidosa, Dunaliella salina, Nannochloropsis oculata, Haematococcus pluvialis, and the diatoms Amphora coffeaeformis in the mitigation of toxicity signs and negative impacts of some aquatic toxicants in the exposed freshwater fish. This will spotlight the strategies based on the use of natural additives that can attenuate the negative impacts of contaminants in farmed fish. The data and literature would be valuable to provide important insights and new references for upcoming studies.