They will eat bloodworms but I will tell you this too much protein puts them at a risk of death. Experienced it myself when I first got into BN plecos lost my first two bn that way. Researched and talked with a local breeder. They are omnivorous and will eat almost all food you provide it. But if it consumes too much protein it will get them bloated and that can be fatal. So don't house bn plecos with other fishes with a higher protein diet. A lil bloodworm on occasions is ok but should always be cautious. I personally avoid it and keep it only algae waffers, veggies, and drift wood.