Congenital Nanoparticles are found to be reactive because of their small sizes leading to a high volume surface ratio which in turn leads to a lot of binding sites for metals and other compounds. The toxicity of nanoparticles depends on the shape, size, structure of the particle and aggregation. The aggregation, in turn depend on different types of factor in the aquatic environment such as pH, organic matter, ionic strength and composition. Bioassay studies (Acute and sublethal toxicity) were identified in fish Cyprinus carpio and the changes were observed. The lethal concentration LC50 for freshwater fish Cyprinus carpio were found to 0.1ppm. Silver nanoparticles were exposed for 24 and 96h and the values were noted as 1.0 and 0.5ppm. During the toxicant exposure various changes were observed like increase of mucus secretion, neurobehavioral changes, DNA gets damaged, the heart rate were increased, the liver cells, the stem cells and the swim bladder were affected. The growth and reproduction were stopped and the sterility were existed in fish Cyprinus carpio due to the exposure of Silver nanoparticles.