It is not uncommon to find worms in swimming pool water. Unless they are a earthworm that accidentally fell into pool, the worms are most likely horsehair or Gordian worms, which are parasites that develop in the bodies of grasshoppers, cockroaches, beetles and crickets. Although they are harmless, most pool lovers will want to remove the creatures. Using the same techniques that you would use to remove dirt and debris, you can safely get rid of the worms in your swimming pool.
Skim the pool with a leaf skimmer. Whenever you see the worms, especially if they are floating on the surface of the water, catch them in the net of the leaf skimmer. Gently tap them on the ground next to the pool so that they fall out of the net.
Vacuum your swimming pool. This remove dead worms on the bottom of the pool that you may not be able to reach with the skimmer or with your own hands. When you are finished vacuuming, make sure that you check the vacuum's filter so that you can remove the worm bodies. They are not dangerous, so you don't need to worry about touching them.
Check your pool's filter. When you run your filter pump, some worms can get trapped in the filter. If you see worms in the filter, remove them.
Collect the worms in a sealed container if you want the worms to be identified. Many university extension or diagnostic services will identify the worms for you if you mail or deliver the worms in a sealed container. Fill the container with alcohol so that the worms don't get brittle. The price for this identification varies depending on the university, but is usually around £6, as of February 2011.
Prevent worms from getting into your pool by properly securing it with a pool cover.
Most worms that get into your swimming pool are harmless, but if you are unsure of the worm, then use protective gloves when touching them. Do not use insecticides in your swimming pool water to kill the worms, as it could be harmful to those swimming in the pool and also disrupt the chemical balance of the pool water.