I spot feed shrimp every 2 - 3 days
I also feed to the entire tank a mix of cyclop-eeze, shredded shrimp, minced garlic, and various sizes of rotifer golden pearls. Occasionally DT's Phytoplankton.
The brains will accept shrimp that is when I spot feed small pieces, so it doesn't seem to be related to food, unless there is something that the brains require that I am not providing.