These creatures cruise along the top of the water and eat algae and other small insects that are located at the top of the water.
Freshwater Snail (Gastropoda)
These animals are tolerant of pollution and just feed on the remains of dead creatures that have fallen to the bottom of the river or stream.
Flatworm (Platyhelminthes)
Flatworms are very tolerant of pollution and stick to the rocks in the streams and rivers so they can feed on dead plants and insects. They have their own method of breathing in which they don't really need to have a lot of dissolved oxygen.
Water Boatmen(Hesperocorixa castanea)
They feed on aquatic plants and algae but can prey on smaller insects if necissary. They swim upside down on the surface of the water and are very tolerant to pollution.
Fresh Water Slater (Isopoda)
These do not like to stay in one place. They are often carried away by plants, animals, floods and other forces to different bodies of water constantly. They can survive just about anywhere.