The book provides a brief description of the role of arsenic as a toxicant and its role in different health of fresh water fish Channa punctatus. The optical microscopic evidence of histopathologycal alterations of Gill, Liver, Kidney and intestine tissues of Channa punctatus exposed to sub-lethal concentration of sodium arsenite for different interval of time are discussed in details. Details discussion on behavioral changes of Channa punctatus under different concentration of sodium arsenite are also presented.