Foul smell in water bodies like tanks and ponds is due to
Eutrophication is a natural state in many lakes and ponds which have a rich supply of nutrients. This leads to decomposition of nutrients through bacteria and other decomposers. The decomposition of huge amounts of biological mass creates a condition wherein carbon dioxide and carbon monoxide are produced and released to the atmosphere. This also emits foul odours which are unpleasant to public convenience.