Just like any other aquarium it's very important to ensure a safe living environment for your axolotl(s). Tank cycling can be confusing for many new owners. In an ideal situation, it would be best to start the process before purchase.
Cycling a new aquarium can take anywhere from 4-6 weeks but everyone's cycle is different. We encourage you to research tank cycling if you don't know how. One can find many well informed step by step axolotl tank cycling guides just by doing a quick internet search. There are several different ways to do it and what works for some might not work for you :) Need help? Just ask.
The cycling process is measured by ammonia and nitrite levels. Many people choose to kick start the cycle with a product such as "Dr. Tim's ammonia" and some nitrifying bottled "good" bacteria. The axolotl has a heavy bioload--much larger than an aquarium full of fish. So you need to be dosing the tank with ammonia to 4 ppm. This simulates the waste your new friend will be producing.
You MUST invest in an API master test kit. The test strips are not accurate enough for an axolotl owner's needs. When testing water parameters, it's considered safe to add your axolotl when the ammonia level finally reaches zero. Hooray!
Then, you want to be performing 25% water changes around once a week to keep the nitrates low. When performing water changes, you should be using a water dechlorinater/conditioner. My favorite is "Seachem Prime" which you can buy at any pet store or on Amazon. The reason why I use this one is because it does not contain aloe. Aloe is dangerous for your amphibians.
If you want to house more than one axolotl in the same tank, do it gradually. Ideal water parameters for an axolotl are the following:
pH = 7-7.5 (can tolerate as low as 6.5, or as high as 8, but not ideal)
Water hardness/GH = 140-250 ppm/8-14°
KH/buffer = 53.7-143 ppm/3-8°
Ammonia levels in a successfully cycled tank should be = 0 (up to 0.25ppm for short periods)
Nitrite levels should also be = 0 (up to 0.5 ppm for very short periods)
Nitrate levels can fluctuate between = 0-40 ppm (however must be higher than 0 to finish cycling in the beginning).