Probably adjusting.
Mine were not fussy. I made no special effort to feed them. Threw in a variety of foods for everyone in 120 gal, which was about 100 fish of 50 different kinds - pellets, flakes, cut fish, shrimp etc. They were not gluttonous IIRC but neither gave me any problems.
I'm getting fuzzy but IIRC they preferred meaty foods - fish, shrimp, etc.
One can trust a Pimelodus pictus catfish in a koi pond. For one. Cory come to mind too. Or a full grown RTC with full grown arapaimas and pacu. You continue...