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Common axolotl myths

Myth #1: Bare bottom tanks cause axolotls to slip and become stressed

A bare bottom tank is a good indicator of current strength. If your axolotl is slipping on the glass, your water flow is too strong. Your axolotl should be able to walk along the bottom of the tank without sliding or slipping.

Myth #2: Sand causes impaction in adult axolotls

The use of sand may be risky for axolotl larvae, but there are no documented cases of impaction caused by sand in adult axolotls. However, impaction cases caused by gravel ingestion in adult axolotls are frequent. Which brings us to…

Myth #3: Gravel is a safe substrate for axolotls

Absolutely not! Remember: if it’s smaller than their head, they will ingest it; if it’s larger than their poop, they won’t be able to pass it!

Myth #4: Goldfish are acceptable tankmates for axolotls

Although they both enjoy similar water conditions, these two species are not a good match. Axolotls are not very good at catching fish, but given the chance, they will eat any fish that fits in their mouth. Goldfish aren’t safe for axolotls either, as they tend to nip at their gills. Their bones can also cause impaction due to their size.

Myth #5: You don’t need to feed your axolotl as long as you keep fish in the tank

Again, axolotls are not good hunters. If live fish are the only option on the menu, they will most likely starve.

Myth #6: Frozen bloodworms are an acceptable staple food for axolotls

Bloodworms are a fatty, low-protein snack. Think of them as the french fries of the aquatic world. Axolotls who are fed nothing but bloodworms for an extended period of time become emaciated and tend to bite off their tankmates’ limbs.

Myth #7: Indian almond leaves work as a painkiller for axolotls

Unfortunately, indian almond leaves have no effect on pain. The tannins they release do have mild antibacterial and antifungal properties, however.

Myth #8: If you see fungus on your axolotl’s gills, you should pull it off or remove it by rubbing it with a Q-tip.

Please don’t do this! By pulling out the fungus, you are literally ripping out living flesh, which is extremely painful. Just allow the fungus-infected gill tissue to necrotize and fall off on its own.

Myth #9: It’s okay to use fish antibiotics on axolotls as long as you use half-doses

First of all, you shouldn’t use antibiotics on an axolotl unless you know which bacteria you are fighting against. If you suspect that your axolotl has a bacterial infection, please ask a veterinarian how you can send in a sample for identification.

Secondly, there is no guarantee that a fish-safe medication will be safe for axolotls. Unless a scientific article or veterinary account confirms that a medication is safe to use on amphibians, please assume that it isn’t!

Finally, by reducing the dose of the antibiotic, you run the risk of creating new strains of antibiotic-resistant bacteria. When treating with antibiotics, always follow dosing instructions and administer the treatment for its entire duration, even if the symptoms are gone.

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Axolotl Diseases

This is a quick reference list of common health issues, as well as axolotl-safe treatments. I will add to this article little by little. If you’d like me to talk about one illness in particular, please email me.

Ammonia poisoning

Deformation of the caudal fin and bleeding due to ammonia poisoning.

Early symptoms:

  • Lack of appetite
  • Curling, atrophy of gill filaments
  • Irritated skin (some redness visible on axolotls with pale skin)
  • Veins becoming more visible (also on axolotls with pale skin)

Advanced symptoms:

  • Whitening, curling, atrophy of gill stalk tips
  • Prounounced red patches on the skin (visible on axolotls with pale skin)
  • Loss of gill filaments
  • Deformation of the caudal fin
  • Erosion of the tail tip and fingertips
  • Bleeding
  • Death

How to diagnose:

In the presence of some or all of the above symptoms, test ammonia levels. If any ammonia is detected, the animal is almost certainly suffering from ammonia poisoning.


Ammonia poisoning is either due to new tank syndrome or improper husbandry (infrequent water changes, overcrowding, overfeeding, or using inadequate filtration).


If the cause is new tank syndrome, follow the treatment instructions listed below. Otherwise, you will need to find the cause of the problem and fix it. Daily 50% water changes and the addition of conditioner every 24 hours will keep your animals safe until the issue is resolved. Keep testing the water for ammonia every 24 hours until no more ammonia is detected. To prevent the situation from reoccuring in the future, I highly recommend testing ammonia once a week.

New tank syndrome

Early symptoms:

  • Gradual loss of vitality, typically within the first month following the introduction of the axolotl to a new aquarium
  • Red patches on the skin (visible on axolotls with pale skin)
  • Curling, atrophy of gill filaments
  • Lack of appetite or inability to chew or swallow food
  • Change in gill color (paler or more brownish)

Advanced symptoms:

  • Whitening, curling, atrophy of gill stalk tips
  • Loss of gill filaments
  • Erosion and/or deformation of the caudal fin
  • Bleeding
  • Death

How to diagnose:

In the presence of some or all of the above symptoms, test ammonia, nitrite and nitrate levels. You can assume that the animal is suffering from new tank syndrome ammonia and/or nitrites are detected and one or more of the following statements are true:

  • Nitrates are absent or very low (~10 ppm or less)
  • The animal has been living in the aquarium for less than two months
  • The filter is brand new, or the filter media has been completely replaced recently
  • The filter stopped running (e.g. during a power outage) for three hours or more
  • You have recently treated the tank with an antibiotic
  • You have been refilling your aquarium with tap water, without adding conditioner

If ammonia and/or nitrites are present but nitrates are also high (>40 ppm) and none of the other conditions apply, a more likely diagnosis is ammonia poisoning and/or nitrite poisoning due to improper husbandry (infrequent water changes, overcrowding, overfeeding, or using inadequate filtration).


Uncycled aquarium (lack of nitrifying bacteria in the filter) leading to ammonia poisoning and/or nitrite poisoning.


Daily water changes and addition of conditioner as needed until the aquarium is properly cycled. The addition of seeded filter media or a bacterial additive is strongly recommended.

Nitrite poisoning

Early symptoms:

  • Very pale gills
  • Frequent breathing at the water surface
  • Crowding near the water inlet or air stone

Advanced symptoms:

  • Gills turning brown
  • Uncontrolled floating
  • Lethargy
  • Lack of interest in food
  • Gill damage, gill loss and/or saprolegniosis
  • Eventual death


In the presence of some or all of the above symptoms, test nitrite levels. If any are detectable, you can assume that the animal is suffering from nitrite poisoning.


Frequently occurs as part of new tank syndrome or as the result of a cycle crash (e.g. after a power failure). May also be due to overstocking, the presence of something rotting in the tank, or infrequent water changes.


Daily water changes and addition of conditioner as needed until the aquarium is properly cycled. The addition of seeded filter media or a bacterial additive is strongly recommended. Make sure the tank isn’t overstocked and that partial water changes are conducted at least once a week.

Saprolegniosis (winter fungus)

Early signs of saprolegnia.

Early symptoms:

  • Raised white or grey lesions that have a soft appearance, like cotton wool. Typically start as small circles on the axolotl’s head or gills, then grow larger and merge as the disease progresses.

Advanced symptoms:

  • A fuzzy growth, reminiscent of a dandelion puff, typically on the axolotl’s gills — may appear white, grey or tan to brown as debris accumulate
  • Partial loss of gill stalks
  • Death, if internal organs are affected


Compromised immune system due to stress, reducing the animal’s natural resistance to saprolegnia (a fungus whose spores are naturally present in virtually all water sources). May appear as a secondary infection if the axolotl is already battling another illness.


The visual cues are usually pretty obvious. In the presence of some or all of the above symptoms, your veterinarian may conduct a skin scraping to identify Saprolegnia’s hyphae (a root-like structure) under a microscope.


Eliminate potential stress causes such as improper housing conditions, poor water quality (especially in an uncycled aquarium), high temperatures, aggressive tankmates or strong water flow. If the axolotl is on the verge of laying eggs or recovering after egg-laying, it may help to isolate her and lower the temperature slightly to help her recuperate. The same applies to an axolotl who is in the process of regrowing a limb. In advanced cases, salt baths are recommended.

Short Toes Syndrome

Axolotl suffering from short toes syndrome. Unfortunately, some unscrupulous breeders take advantage of this painful and deadly condition by marketing the afflicted animals as “dwarf axolotls”. Buyers beware! Photo: Amanda Gomes

Early symptoms:

  • Unusually short limbs and toes
  • Inability to regenerate missing limbs
  • Shortened/missing bones and bone joints

Advanced symptoms:

  • Signs of pain and distress (forward gills, mouth hanging open, arched spine, lack of interest in food, lack of movement)
  • Internal bleeding
  • Skin blisters
  • Hemorrhages
  • Extreme swelling and bloating


Short toes is caused by a genetic mutation, which results in skeletal, renal and urogenital malformations. The afflicted animals have shortened lifespans, eventually suffering from painful edema and kidney failure.


The shortened toes are a sufficient cue.


Unfortunately, not much can be done to alleviate the issues caused by the mutation. Studies suggest Holtfreter’s solution may help for a time, but it may be kinder to euthanize the animal to spare it further suffering. Alternatively, you may consider donating your axolotl to a university, as short toes axolotls are important to limb regeneration research.

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Axolotl housing

Proper housing is the key to keeping your axolotl healthy! Please make sure to read all of this before buying an axolotl.

Aquarium size
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.