There are a number of species of earthworms or Oligochaeta . Tubifex are an inch long, are red, and live in tubes in bottom mud. Chaetogasters eat small animals with their large mouths and grow to half an inch. Deros build tubes in debris, grow to about half an inch, and have bristles. Aeolosomas grow to half an inch, live in debris or on plants, and can have colorful spots.
All species tend to stay on the bottom or in debris, dirt, etc.
Flatworms Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. The first two are familiar parasites. The latter move around on surfaces using cilia and eat small living or dead animals. Other turbellarians are also rather harmless. Dugesias tigrina is the largest free-living flatworm, growing to an inch long.