All over the world, attempts are made to avoid use of hazardous chemicals in aquaculture and agriculture systems. To replace them with eco-friendly and degradable biocides, plant secondary metabolites are considered as a potential alternative. This book provides a new insight of use of Cestrum species (Family: Solanaceae) as potent biocide. First chapter deals with the extensive literature survey of this plant. In second chapter, detail procedure for extraction isolation and characterization of Saponins and alkaloids of C. nocturnum and C. diurnum is given. Whereas Detail methodology for the evaluation of piscicidal, insecticidal, molluscicidal, haemolytic, activities of bioactive extracts and compounds on various experimental animal is given in chapter three. Chapter four deals with the protocols for evaluation of mode of toxicity of above bioactive principals to carp fish, using extensive physiological and biochemical tests. Lastly, every aspect of above experimentation and finding is discussed and supported with bibliographic information. This book is of utmost important to the researchers working on the phytochemistry, pharmacognacy, botanist and fishery sciences.