Axolotls are happy to live in a tank alone but they can be housed together too.
We do not recommend keeping them with other fish. This is due to differences in ideal water temperature as the axolotl requires much lower temps than most fish. If housing them together, one will always run the risk of the fish nipping at the axolotl's gills or the fish becoming a snack for the axolotl.
Axolotls CAN be housed together. However, once sexually mature they should be in designated male and female tanks if you own multiples. Even when breeding is intentional, different sexes should only be housed together temporarily for mating to avoid stress and overbreeding of the female. It has been reported that the male will eventually breed the female to death.
If you choose to house more than one axolotl in the same tank, it's good practice to ensure they are well fed at all times to avoid accidents/injuries.