Red Worms in Pool Filter: Bloodworms, Chlorine Resistance, and Elimination

Red Worms in Pool Filter: Bloodworms, Chlorine Resistance, and Elimination

A pool owner finds red worms in the filter (similar to a previous pond question). Chlorine shock didn't eliminate them; they reappeared in the rinsed filter next day. Wants them gone for swimming comfort.

What They Are

Bloodworms (midge larvae) or small earthworms. They live in filter media where organic debris collects. Chlorine should kill them, but eggs or protected larvae may survive.

Eradication Steps

1. Verify chlorine level with a reliable test kit; maintain proper free chlorine (1-3 ppm for pools).
2. Deep clean filter: Disassemble, soak media in strong chlorine solution (10 ppm) for 30 mins, rinse thoroughly.
3. Remove organic debris from pool bottom and skimmers – their food source.
4. Prevent entry: Fine mesh on skimmers, cover pool when not in use to deter midge egg-laying.

Note

They are harmless to humans. In a pond, they're fish food. In a pool, they're a nuisance but not a health risk.