He is used to eating live food. Youll have to strave him for a day or two. Then he will eat the pellets. Also u shouldnt feed him feeders or live worms, they can carry parasites and spread them to your flowerhorn leading to diseases and possibily death. Pellets as a stable and market shrimp, frozen blood worms as a trear are best.
Sent from my SGH-T679 using MonsterAquariaNetwork App