I have two blackfish in aquaria this is the smaller of the two and I just added a dozen freshwater shrimp , and I think he likes them.

Notice he left it until it was in the rocks and then felt it with his barbels.

[wpvideo 4yAZOiug]

In this second video you can see how the larger of the fish tests the worms with his barbels  and when he is happy they are proper food he backs up and eats one.

[wpvideo V7gVRys9]