We have been keeping axolotls for many years, they live outside all year round in old baths.
They have hides & plants but we keep the bottom of the bath bare for easy cleaning.
The outside of the actual bath is wrapped in insulation foam behind wooden side panels.
We used some clear perspex on the back panel and on the lid - which is hinged for easy access.
The fixed side panels have insect mesh on the inside & aviary wire on the outside for protection from predators.
The mesh & wire front panel comes off for easy access - combined with a lift up hinged lid, cleaning & maintenance is quick & simple.
They have constant access to live food, sharing their bath with Daphnia, Asellus aquaticus & other pond bugs. They are also fed with pellets every 3 days.
They have live bloodworm on weekends & we alternate axolotl pellets with Hikari sinking carnivore pellets for variety.
In the winter we use an aquatic heater to keep the water at around 10 - 12*C.