Blackworms are full of nutrients and it's a delicacy that all fish love!
Keeping them alive is crucial. Blackworms do best in darkness, and their metabolism slows if you keep them cool. Blackworms need access to air to be alive when you feed them to fishes. Therefore, keep them in a cool room in a wide white ceramic dish in enough water just to keep them covered.
Before you handle the worms wash your hands with warm water and soap, then completely rinse off the soap.