Enclosures
Axolotls have long endured substandard husbandry by way of overcrowded, undersized enclosures. E.A.R.S. aims to change that. We recommend a large aquarium ‘footprint’ minimum for enrichment, as well as standards that meet or exceed proper stocking requirements.
These animals boast incredible regeneration abilities which biologists study, including the ability to regenerate limbs and parts of their nervous system. Due to this, they have been raised like ‘lab rats’, so to speak, living permanently in tubs they could barely turn around in or being crowded extensively in a large tank after being confirmed as a sexed adult.
E.A.R.S. recommends a standard which meets the UK Herpetological Society's general standards, as translated from similarly sized reptiles (ex. lizards, skinks), as their current standards have not covered axolotls.
This involves taking a measurement of the animal ‘snout to vent', which is an axolotl’s nose tip to cloaca. This measurement is multiplied to determine the approximate required inch measurement of the enclosure.
Currently, the recommendation is
Width = STV x 6
Height = STV x 3
Depth = STV x 3
It is recommended to purchase the appropriate size aquarium needed to house the adult animal, as axolotls usually reach their adult size by around a year old. Axolotls typically grow to around 8-12”, and around 2/3rd of this is their S.T.V. length. Therefore, it is expected to work with 6”.
Content credit of Caty Boulinzann
Axolotl on right raised by Caty Boulinzann in a large enclosure as compared to an axolotl from the same clutch raised in a deli cup.
It’s no secret that being active is the key to a long life, and the CDC recommends that humans partake in 30 minutes of moderate-intensity aerobic exercise per day. This is proven to support cardiovascular health, musculoskeletal health, and prevent obesity along with appropriate nutrition.
The ASPCA recommends 30 minutes to 2 hours of exercise per day, breed dependent, for dogs.
While exercise standards have not, and likely will not, be established for herptiles (most axolotls don't like to play fetch) - they still clearly require an appropriate amount of space to move around in, even if it is shared with other animals.
For axolotls, this means a large ‘breeder’ style aquarium. These tanks are 18” in depth, allowing the typical 9” axolotl to move across twice their own body length, and giving even the rare 13” axolotl the ability to stretch - which is less afforded in a well decorated 12” depth aquarium.
Breeder aquariums rarely come in sizes under 40 gallons, although the seldom found 30 gallon breeder aquarium is perfectly acceptable for a single axolotl. Otherwise, since cycling a tank takes so long (make sure to read our cycling guide!), and because axolotls grow so fast, it's heavily recommended to begin with the aquarium you'll be sticking with in the long run - which will realistically be a 40 gallon or larger.
Cohabitation
Tankmates are a difficult topic, and this particular writing will only go over same-species cohabitation - visit our page on Tankmates to learn more on other species!
Axolotls are considered sexed adults when they either are confirmed as male (cloacal glands swell beneath the tail at around 8-18 months of age), or when they have aged 18 months and not yet shown signs of being male - confirming them to be female.
Unsexed sub-adults and juveniles should never be cohabitated. Sub-adults may be able to breed before they show their reproductive organs visibly, and juveniles have a very fast metabolism, causing them to nip each other with an increased likelihood.
If you have two axolotls in the same tank together already that shouldn't cohabitate, it's a great idea to make a barrier out of nylon window screening - and begin cycling a new tank ASAP.
To cohabitate, two axolotls must be of the same size, or within 2” of each other in body length. Their heads should be around the same size, and they *must* be the same confirmed sex.
Adult male axolotl
Content credit to Adelina's Axolotls
Adult female axolotl
Content credit to Adelina's Axolotls
Nitrates
When deciding on tank size, there typically isn’t much need for concern regarding nitrate levels when using a properly sized breeder tank. However, when cohabitating axolotls, nitrates should be taken into account.
Nitrates should never be allowed to rise above 20 ppm, and should not be sustained above 15 ppm. Ideally, they should remain around 5-10 ppm, sustained via frequent 50% water changes. This results in the fluffiest of gills, the healthiest of immune systems, and the happiest of axolotls.
See our downloadable PDF article at the end of the page to learn more about the toxicity of nitrate!
Always test your source water before proceeding with setting up an axolotl tank - in this case, high ammonia or nitrate in tap water results in an automatically higher bioload and therefore reduced effectiveness of water changes.
Additionally, you'll need to keep in mind that a single axolotl commonly produces around 1 ppm ammonia per day in 20 gallons of water. This is 0.75 ppm in 30 gallons, 0.5 ppm in 40 gallons, and so forth.
Since 1 ppm ammonia > 2.7 ppm nitrite > 3.6 ppm nitrate, as a baseline, this results in around 25 ppm nitrate at the end of the week for the axolotl in 20 gallons of water. Therefore, 20 gallons per axolotl is somewhat overstocked, but manageable still with increased water changes.
25+ gallons per axolotl works best for the average keeper, so long as they begin with at least a 40 gallon enclosure.
Overall, the recommendation of E.A.R.S. is to put enrichment first when choosing an enclosure, and give allowances to nitrate management. If you're looking to cohabitate, get just one axolotl at a time - it's much easier that way, I promise.