Ideas for a small pond

[efs710920mex]

I'm about to build a small pond for axos in a small garden and I could use some advice about some "unexpensive" alternatives. My first idea is using a 5000 water container cut in half and decorated with wood on the outside.

 

[JM29]

Axolotls can be kept outside in various conditions (and Mexico is their origin place).
I have kept some outside at different periods of the year, including winter (with frost) and summer. They thrive well providing they are not overcrowded. I must admit I live in a region never very hot and never very cold. Here are some ideas :

The pond (or container) should be deep enough to avoid complete freezing of the water mass in winter (I don't know the risk in Mexico City)
A 5000 (liters, gallons ?) container looks fine, but what about the dimensions ? Depth particularly ?
Don't put it in full sun because of the risk of excessive temperature rise in case of hot summer.
And no fish ...
Ponds may be sometimes visited by predatory birds like herons, which could be dangerous for axolotls. If the pond is near your house, the risk is weak.