Tubificidae

Japanese: Tubificidae

…They are sold as food for ornamental fish, but there are several species of the Tubificidae family mixed in. The Tubificidae family includes the lily worm Limnodrilus socialis , the white worm Rhizodrilus limosus , and the gill worm Branchiura sowerbyi (illustration), and they have a similar long and slender appearance. However, they can be distinguished by the fact that the lily worm has a pair of male pores on the left and right sides of the ventral surface of the 11th segment, while the white worm has a single pore on the midline of the ventral surface of the 11th segment. …

From 【Earthworm】

... Includes the long-legged worm, the staghorn worm, etc. The Tubificidae family of worms gather in large numbers in the mud of sewage to form clumps. They include the tubifex worm, the lily worm, the gill worm, etc. ...

*Some of the terminology that mentions "Tubificidae" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…観賞魚の餌として売られているが，これらの中にはイトミミズ科に属する数種類のものが混在している。　イトミミズ科TubificidaeにはユリミミズLimnodrilus socialis，シロイトミミズRhizodrilus limosus，エラミミズBranchiura sowerbyi（イラスト）などが含まれ，細長い外形はよく似ている。しかし，ユリミミズは雄性孔が第11体節の腹面左右に1対あるのに対し，シロイトミミズは第11体節の腹面正中線上に1個あることで区別できる。…