I have small ... very very small white worms in my sump because I sometimes place old sword leaves in it. If I stir the sump a bit these worms go up into the aquarium where all my fish devour them quickly. OK so I've been doing this for years and my fish, especially my Black Phantoms are in incredible sparkling shape. I haven't gotten a case of ick or any other kind of sickness in years. However they do die of old age after about 5 years or more (they become very droopy and just wither away). And, I feed them brine shrimp and flakes and the occasional summertime Daphnia from a farm pond. They aren't glass worms though like the pic in the replies. The worms feed on the dead leaves I put in the sump next to the sump pump. Could these be the worms you have? If they are I wouldn't worry too much. My advice to you would be to feed one very small pinch of food twice a day for every twenty fish. And skip weekend feedings. Keeping them hungry for awhile is healthy for fish (This last step is only recommended for non-agressive fish ... mine don't nip each others fins!)
And, yes, reducing the food rations will help reduce their numbers.
