Tubifex
From Microcosm Aquarium Explorer
Family: Tubificidae
Species in Genus Tubifex:
Also called sludge or sewage worms, Tubifex worms are small worms that are eaten greedily by aquarium fishes.
The species involved is usually referred to as Tubifex tubifex but there are likely different species waiting to be identified.
See: Tubifex Worm.