Augie, good thinking on trying to pellet train those RES. Until the Optimal arrives, offer them anything and everything you can get your hands on-yes, minced shrimp and fish, red wigglers, minced earthworms or nightcrawlers, mealworms, aquarium tropical fish food, crumbled moistened cat food, etc.
Do you have any other pellet feeding fish in the pond that you could catch and place in the cage to show the RES what It's all about? I put several fingerling GSF in an aquarium last year. They wouldn't eat anything for a couple of weeks. It seemed they were going to shrink down to nothing and starve. I added feeder goldfish who encouraged the greenies to try pellets, etc. Now they're all voraciously gobbling feed.
If you have vegetation in the pond that has snails crawling it, pull up some plants and stick some sprigs of that in the cage. You might put something solid on the bottom of the cage, such as plastic or metal, that would stop the food from falling through the mesh. This would give the fish more time to inspect the particles as they lay on the cage "bottom".
Remember, RES are low light feeders, so shade over the cage may help.
I'm probably reinventing a wheel that is already spinning, but these are some of my random thoughts.
Good luck.
