Is the RD just eating all the food? Or chasing the other fish away from it?
For my piggy-fish, I’ve been successful with meatier foods— they fill up the mouth and gullet (idk fish equivalent to that) faster and more effectively than concentrated pellets which expand later in the body.
the other fish get to eat while the piggies are all, “aww man, I can’t fit anything else”.
My favorites are crickets and mealworms and roaches (you can “gut load” them with whatever food you want the fish to be eating), but shrimps and frozen fish work well, too (but more expensive).
For large fish, setting up a roach colony might be a beneficial, money-saving option, and is relatively simple. Some of my larger species of cockroaches get 2.5” and are meaty AF. Feed off the males, and the colony just keeps producing for you.