Ethical Axolotls

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 tank after being confirmed as a sexed adult.

We reviewed the standards which meet the Federation of British Herpetologists’ husbandry requirements, 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 * 6

Height = STV * 3

Depth = STV * 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 can grow to around 9-12”, and around 2/3rd of this is their S.T.V. length. 2/3rd of 9″ is 6”, and so the calculations are typically 6*6, 6*3, 6*3. This results in a recommended tank size of around 36″ x 18″ x 18″. Interestingly enough, a 40 gallon breeder measures 36″ x 18″ x 16″ – it’s a match made in heaven, in terms of floorspace! If you want to learn more about reptile husbandry recommendations, visit the FBH here.

Content credit of Caty Boulinzann

The axolotl in right tub was raised by Caty Boulinzann of Siserah’s Aquatic Escape, in a large enclosure. As compared to the axolotl on the left, which is from the same clutch but raised in a deli cup by another individual.

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 (which is the measure of the aquarium from front to back), 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. Aquarium height is very unimportant for axolotls.

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 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 cohabitants. I personally view axolotls as a species-only pet, however, they can cohabitate with their snacks, such as ghost or cherry shrimp.

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. Occasionally a female will go through an obvious gravid period before 18 months of age, however it is difficult to differentiate between a plump unsexed male, and a young gravid female.

Unsexed sub-adults and juveniles should not 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. 

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 large water changes. This results in the fluffiest of gills, the healthiest of immune systems, and the happiest of axolotls.

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 what your individual axolotl will produce.

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 an axolotl producing 1 ppm daily – making 1 ppm ‘overstocked’ for weekly water changes. Typically, an axolotl does not produce this much ammonia in a 20g aquarium, on its own. However, lack of spot cleaning, leaving uneaten food to decay, or hidden debris/poop can result in ammonia spikes, which in a cycled aquarium results in excess nitrate. If you are comfortable performing multiple water changes in a week, a 20 gallon aquarium would not negatively impact the well-being of your axolotl. If you prefer to have fewer water changes, a 40 gallon is a great choice for your first axolotl.

If your animals are the same size and sex, they can usually be cohabitated in almost any breeder aquarium.

20 gallons per axolotl works best for the average keeper, so long as there is plenty of floorspace and filtration. If you’re unsure, opt for a larger aquarium – these animals can live 15+ years, so their long-term comfort and your long-term enjoyment of the hobby depend on having enough flexibility.

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, and add additional inhabitants down the road – it’s much easier that way, I promise.