Minecraft wiki entry for Axolotl_farming, associated text: To gather axolotls, go through the back door with buckets of water. Even though the hallway is pitch dark, once you pass through the door into the water, your underwater vision is sufficient to see axolotl in the room and catch them in your water buckets. An axolotl may wander out the door into the hallway. That's OK, you can still catch it. If you want to keep axolotls around, you need to interact with them (feed them, breed them), otherwise they may despawn again.