The problem with goldfish is they are too high in fat, minnows are better for them when you want to feed fish.
Have you tried any live bugs? My aquatic turtles love live crickets, mealworms, superworms, wax worms, June bugs, grubs, and one of them will eat roaches the other won't.

Check your pellet labels, some of them have wheat gluten in them & I know from searching websites like itchmo & the AVMA that some fish foods & a ferret food have been pulled because of wheat gluten. I don't trust ANY food that has wheat gluten or rice protein in it at the moment.. not with all this recall stuff still going on even though it's not reported on the news much anymore.
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PHRatz