In Minecraft, axolotls love eating Buckets of Tropical Fish. After feeding an axolotl, hearts will display around the creature, which means the mob is not only happy, but ready to breed with another axolotl.
Tropical Fish can be found in oceans, specifically in warm biomes, and there are multiple varieties of tropical fish with various colors and patterns to look out for. To collect a tropical fish, the player must have a bucket equipped. While approaching the tropical fish underwater, use the bucket and/or press right-click to scoop the tropical fish into the bucket.
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If the player intends to breed axolotls, they will need at least two Buckets of Tropical Fish. Only feeding one axolotl will not entice it to breed with another axolotl. Both axolotls must be fed tropical fish in order for them to breed a new baby mob. The process often takes a handful of seconds.
Axolotls are amphibian mobs that released in part one of the Minecraft 1.17 Caves & Cliffs update. These aquatic creatures can be found in underground water areas, or below sea level in total darkness around y63. Axolotls are also expected to spawn in Lush Caves when these biomes launch in the Minecraft 1.18 update.
Although axolotls cannot be tamed or domesticated, players can still construct a gated pool near their spawn area to provide these creatures a home. To transfer an axolotl from its spawn location to the player's intended location, the player must have a bucket of water. Picking up the axolotl works the same as the tropical fish: approach the axolotl and use the bucket to scoop the mob into the bucket.