Wow, those are some picky eaters, Snipe!
I would think at some point they would get hungry enough to eat something besides their preferred food ... which shows how little I know about feed training fish.
I am sure you have tried everything, but I will throw out one potentially stupid idea.
There are lots of examples in nature of an individual animal that has learned a beneficial behavior and it teaches that behavior to other animals in its group. What would happen if you tagged one of YOUR SMB that does readily eat pellets and put him in the tank with the picky eaters? When they observed that fish popping the pellets, might it induce them to also pop the pellets?
There's 700 fish in the same tank, a mix of mine and the other source fish. Very few have learned by example, wish it was that simple but it hasn't proven to be so..
