Worm-like critters in small pond atop insect tower

Worm-like critters in small pond atop insect tower

Observation - Worm-like critters in small pond atop insect tower - UK and Ireland. Description: Hundreds of 'worms' seemingly attached to the bottom of this very small pond (in which there are no fish, tadpoles, water boatmen)wriggling and writhing. Approx.1cm in length (may be a bit more). They retract when touched.

Hundreds of 'worms' seemingly attached to the bottom of this very small pond (in which there are no fish, tadpoles, water boatmen)wriggling and writhing. Approx.1cm in length (may be a bit more). They retract when touched.