Hmnm. Running a pump isn't an option which still leaves the cage approach somewhat inconvenient (no dock).

I'm not trying to be difficult (comes naturally), but the feed training isn't the main goal. Primarily I want to collect adult GSF so that when the new pond is ready I can tag them and add them in one move.

Even if they weren't taking pellets very well initially, they will be exposed to it regularly in the new pond. I know that RES aren't usually pellet feeders, but can you count on other lepomis to come around to it eventually without specialized training techniques?