Numerous species (Platyhelminthes)
Not really used as food very often as not to many fish eat them, included for completeness with other worms as they show up not inferentially in aquaria. See Sluys, R.; Kawakatsu, M.; Riutort, M.; Baguņā, J. 2009: A new higher classification of planarian flatworms (Platyhelminthes, Tricladida). Journal of natural history, 43: 17631777. doi: 10.1080/00222930902741669