Not eating pellets?

I got a better fish maybe 2-3 weeks ago and he doesn’t eat the slow dropping fish pellets. He freaking loves frozen brine shrimp and his tank mate(who I didn’t know was in there) Ruby the shrimp. Is this a common thing? It’s never happened to me before

He is currently in a 5 gallon tank by himself until I move in a couple months and clear out the 29 gallon tank. Might add a nerite snail to eat the rest of his food he doesn’t eat at night.