Strange how fish get so well trained with a particular feed type that they won't feed any other way.
I used to use sinking pellets in the early days, then swapped over to floating pellets when I found a cheap source of bulk feed. Now my silver perch, murray cod and black bream that had been raised on a sinking diet refused to come up to the surface for the floating pellets. I was worried that they weren't getting enough to eat, but they survived ok even though I never saw them eat anything. I guess the pellets would eventually begin sinking and they would catch them on the way down.
When I bought some barramundi fingerlings for the large system, I decided to throw a couple of barra into the tank with the other mixed fish. Now the Barra had been raised on a diet of floating pellets, so when I threw the feed into the mixed tank, they came to the surface as they always had, and the others seemed to miss out.. Over a week or two I noticed that the silver perch and black bream were starting to come to the surface as well when I threw the feed in, they had been learning from the couple of barramundi, that if you came up to the surface you'd get a feed...
So after maybe 6 months of never seeing any of the fish eat the pellets from the surface of the water within a couple of weeks they were all feeding at the surface, they just needed to see how it was done..
I guess this is an important aspect for people to remember when buying fish, ask what type of feed the fish are used to eating, sinking or floating, it can make a big difference.