Your pet axolotl will be happiest and live longest if you get the water parameters right. Axolotl prefer temperatures of low to mid 60 degrees Fahrenheit. Temperatures up to 68 are well tolerated. Temperatures above 74 degrees will lead to stress, lost appetite, and may even lead to death. Tank chillers are available, but these cost hundreds of dollars. Just make sure you are able to provide a water temp within an axolotl preferred parameters, and make sure you can do it consistently! If you live without central air, or some other form of thermostat controlled environment, then an axolotl may not be the pet for you.
Make sure you cycle your tank before introducing your axolotl to the water.
Water can be tested with API Freshwater Master Kit; this kit is highly recommended as it tests all the necessary water parameters and is highly accurate. The water test kit comes with easy to read instructions, test tubes, can perform eight hundred tests, and includes a color chart for easy to understand results.
Ammonia and Nitrite need to be ZERO parts per million (PPM) as they are toxic to axolotls.
Nitrate should read between 5-20 PPM. If the nitrate level is too low the cycle breaks down. If it is too high it is toxic to axolotls.
PH should ideally be between 7.4-7.6 on the PH scale. Axolotl can tolerate a PH level 6.5-8, however water outside the ideal ph parameters can lead to ammonia toxicity.