We have used feed trained LMB from 5 different hatchery sources from 2 inches to 12 inches. While some may still eat a few pellets - none as far as I can tell have stayed on feed. The natural forage is too big of an enticement. I do think a few non-trained LMB have learned to eat pellets but my guess is under 1 %. You would have a better chance of keeping LMB on feed in a pond if you stocked them as young adults that were eating big pellets when you put them in an keep the same routine. A small closed system is different from a pond with lots of forage swimming around.