Axolotls in Minecraft only eat buckets of tropical fish. Because in real life, Axolotls only eat living fish, so the Tropical Fish food item in Minecraft is considered as a dead form of tropical fish.

Axolotls are the first mob in Minecraft to eat tropical fish. But in order to breed the axolotls, you actually need a bucket of tropical fish, not the fish itself. For a detailed guide, you can check ...