I thought this was interesting to read after seeing only my Catfish and Pleco go for beef heart. Although none of the other fish care for it, they tear it up. Along with that, one of my Severums absolutely loves freeze dried shrimp and eats them whole before other fish even know they were in the tank. I'm starting to think that fish may have preferences for different foods (ones that are in their normal diet, i.e. different brands of flakes, pellets, shrimp, and different types/brands of meats).
http://mentalfloss.com/article/66406/can-fish-taste
http://mentalfloss.com/article/66406/can-fish-taste