The tropical environment is unique due to its geographic location, climatic features, intense solar radiation, high temperature, heavy precipitation, less seasonal variation, enhanced food and productivity, faster metabolism, ecological dynamics and co-evolutionary processes that favor niches for specialized species. It also provides the richest biodiversity with endemic fish species that support millions of people in rural areas. This book Aquatic Sciences in the Tropics: Inland Waters, Domain and Nutrient Geochemistry comprises nine primary chapters that address various topics. Chapter 1 covers topics such as Water as a Substance, Water as a Medium, Fundamentals of Global Water Distribution and Hydrologic Cycle, Economics of Water and Challenges; Chapter 2: The Environment, Tropical Environment, Concept of Biosphere and Aquatic Biome, Tropical Aquatic Bionetwork, Tropical Limnology; Chapter 3: Origin of Lakes, General Classification of Lakes, Tropical Lakes, Lake Morphometry, Morpho-Edaphic Index, Trophic State Index of Lakes, Wetlands, Mangroves; Chapter 4: Concept of Stream Order, Streams and Rivers, The River Continuum Concept, Physico-chemical and Biological Features of Streams, Adaptations of Hill Stream Fishes; Chapter 5: Light as an Entity, Thermal Regime, Thermal Stratification, Lake Mixing, Turnover and Circulation; Chapter 6: Sources of CO2 in Inland Waters, Hydrogen Ion Concentration, The CO2–CO3–HCO3 System, Alkalinity, Hardness; Chapter 7: Dissolved Oxygen, Oxidation and Reduction Potential; Chapter 8: Total Dissolved Solids, Dissolved Organic Carbon; Chapter 9: Origin of Atmospheric Gases, Carbon and Carbon Cycle, Nitrogen, Nitrogen Fixation, Ammonification, Nitrification and Comammox, Denitrification and Anammox, Phosphorus and Sulphur. It is anticipated that the academic community, students, teachers, instructors, researchers, colleges, universities, institutions, administrators, policy makers, public libraries and the general public with an interest in these topics will find this text to be a valuable source of information and provide in-depth knowledge.