Axolotls are a type of salamander native to two lakes in present day Mexico City, Mexico, and named after Xolotl, the dog-headed Aztec god of fire and lighting. Axolotls remain in the larval form their entire lives, resulting in external gills even as an adult. This condition is known as neoteny and is relatively rare in the animal kingdom. Axolotls will spend most of their time on the bottom of the aquarium, but water levels should remain below 18" to allow easy access to the surface, and be sure to have a secure lid to prevent escape.