I wrote some on this and was taken away. Upon return I read ewest's reponse which is a much better explanation than mine.
I don’t have any experience with aquarium fish so I can only draw from the pond. I started with 100 tilapia, all “pellet trained”. If I feed the tilapia veggies they eat just as Eastland describes. But, feed them pellets and they strike eagerly as the pellets hit the water. They then settle down a little, but still try to get as many pellets in their mouth as possible. Live crickets are some where in between.
One other thing would seem to be a factor, fish that feed on live fish would need to be a lot more aggressive than fish that eat algae, I don’t see many fish racing to down that last little bit of algae. My little water snake never goes for the pellet.
After reading ewaet's response, I don't know if this in any way helps, but sparrows, a seeded eater, will eat insects just prior to laying eggs. The chicks need more protein.
