If you can climatise your axolotl gradually, then you may be successful. My temperature in my tank can drop by 10 between day and night and then obviously rise by 10 when night becomes day. So if i was going to do what you are suggesting, i would wait for my night time temperature drop, and then before my temperature begins the daytime rise, i would see if i could keep the temperature down, maybe even fridge to stabilise at the lower nighttime temperature, leave in the fridge for the day, and then if you can, lower the temperature in your fridge over night, by 2-4 degrees max or gradually to the tmperature of your outside pond, keep that temperature stable for at least 12 or more hours, your axolotls metabolism will slow down and i would imagine it will have less of an appetite, check the general condition of your axolotl, and if he still looks ok, i would start adding small amounts of pond water to your axolotls container, over a few hours and then you should be ok to release him into your pond. Maybe there is other ways to do this, i'm sure there will be, so hopefully others will post their methods, then you can decide which will seem the best for you to try. Hope this helps.
