Proper housing is the key to keeping your axolotl healthy! Please make sure to read all of this before buying an axolotl.
You will need a minimum of 10 gallons of water per axolotl. Remember, your axolotl will grow to a length of 10″ or more! If possible, get a longer tank rather than a tall one — axolotls spend most of their time at the bottom of the tank. Make sure they always have room to walk around and turn comfortably.
Axolotls prefer very slow-moving water and will become stressed to the point of illness if the water flow is too strong. They are very light and easily pushed around by the current. For this reason, I strongly advise against using a HOB filter (hang-on-back filter, power filter). The safest filters for axolotls are poret filters, box filters and canister filters with adjustable flow. If you decide to go the canister route, make sure to cover the intake with a sponge. No matter which filter you choose, you will need to provide a source of biological filtration. Just like fish, axolotls are prone to new tank syndrome, which means proper cycling is absolutely essential. If you’re not sure what any of this means, please read this: Introduction to the Nitrogen Cycle (Or, Why You Killed That Goldfish When You Were Little).
Substrate (or not?)
Axolotls do just fine in a bare-bottom tank. I personally prefer to keep my tanks bare, as it is easiest to clean. If you prefer to use a substrate for esthetic reasons, keep in mind that sand is dangerous for axolotl larvae, and gravel is dangerous for adults. If you want to use rocks, use large, smooth pebbles or river rocks that your axolotl won’t be able to eat. Axolotls are like babies: if it fits in their mouths, it will end up in their mouths!
Axolotls like to explore their environment, so it’s a good idea to switch up their decor once in a while to keep them entertained. They like to have objects to climb, floating items to cling to, and places to hide. Pvc pipes, clay pots, caves and driftwood are all appreciated. Make sure all of the decor pieces are smooth, and too large to get accidentally swallowed. Plants are fine (plastic or live). Axolotls are carnivorous, so they have no interest in eating live plants — they just enjoy hiding in them or clinging to them for support. I recommend getting the floating kind, as they also provide shade, and will stay out of your way during water changes.
Lighting (or not?)
Axolotls don’t particularly need lighting, and will shy away from bright lights. They don’t have eyelids, which makes them easily blinded by sudden light changes. Their vision in general is poor, and they hunt largely by following smells and reacting to movements in the water. If you need to use lighting for plant growth or picture-taking, just make sure you provide your axolotl with some shaded spots to hide in.
Axolotls are subtropical animals, which means they should never be kept in a heated aquarium. They can handle temperatures between 4 and 22°C, with 15 to 18°C being their preferred range. At 23°C, they start to get uncomfortable and often refuse to eat. At 24°C and above, the stress can cause them to get physically ill, and eventually cause death. If possible, try to keep your aquarium in a cool part of the house. During summer, you may need to cool the room down with air conditioning. A regular desk fan may help lower the aquarium’s temperature by a few degrees. If this isn’t sufficient, you may need to purchase an aquarium fan or chiller.
Cover (or not?)
Axolotls rarely jump out of their aquariums, but it can happen, especially if they are in a cramped space. If you choose not to use a cover, make sure the water level is low enough to discourage jumping.