• Larva of stone fly: These organisms are highly sensitive bio-indicators of water quality. They require cool, clean, and well-aerated water with high levels of dissolved oxygen to survive. Because polluted water typically has low dissolved oxygen (high BOD), these larvae cannot survive and are therefore absent.

• Hydrilla & Water hyacinth: These are aquatic plants that are often tolerant of or even thrive in nutrient-rich, polluted waters.

• Blue green algae: These frequently flourish in polluted waters, leading to algal blooms due to high nutrient loads (eutrophication).