It comes strongly advised to not house an adult axolotl in a 10-gallon tank permanently. This is not sufficiently sized to meet their needs. This is especially true in 10-gallon tanks that have a lot of horizontal space. However, they could be housed there temporarily, such as during the cleaning of their regular and larger tank. It must also be said that a smaller, younger juvenile Axolotl (shorter than 4-5" in length) may be able to be kept in a 10-gallon tank for a short while, or at least until they begin to grow into their adult size.