Personally, I don't feed aquatic worms. There is too much of a chance to introduce aquatic diseases and parasites. I would use terrestrial worm (whiteworms, earthworms or Grindal worms) instead. If you do decide to use worms, because they are excellent sources of proteins and fats, I would suggest feeding them only 2-3 time a week. Overfeeding worms - aquatic or terrestrial - causes fatty deposits in the fish.