They should be fed as a treat, once or twice a week. Bloodworms have a chitinous head that can become lodged in a fish's intestines, particularly fish that normally eat plants since their intestines are curved instead of straight.
Honestly, you don't need to feed bloodworms, feed chopped earthworm instead. It's highly nutritious, and as an added benefit of being fresh, all of the nutrients that are normally lost in the commercialization process, are preserved.