Floating photovoltaics FPV systems are a renewable energy source that has been proposed as a potential solution, especially in areas with limited land and rising energy consumption. This review analyses the international opportunities for reservoir-based floating solar farms and measures their effects on aquatic ecosystems in recent literature (2018-2025) and in global FPV datasets. FPV systems have a cooling effect of water, which makes them 5% to 10% more efficient than land-based solar systems. The evaporation losses can be reduced by covering less than 15% to 20% of the total reservoir area without interfering with the ecological conditions. However, insufficient coverage can change thermal stratification and light penetration, dissolved oxygen dynamics, and nutrient cycling, which can affect aquatic biodiversity. Key gaps in ecological monitoring, material sustainability, and policy frameworks are found in developing regions. The results highlight the importance of standardizing environmental assessment procedures, combined with techno-environmental planning and policy development, to achieve the sustainable implementation of FPV systems. In general, reservoir-based FPV is an option that opens a new opportunity to increase clean energy production without adversely affecting water resources or their ecosystem reliability.