Axolotl Care Guide
Authors:
Silvia Ochoa, Adam Mickle, and Karlie Bullivant.
The axolotl (Ambystoma mexicanum) is a fully aquatic salamander species, native only to Lake Xochimilco and the extinct Lake Chalco of Mexico. The unique freshwater lake system in the Basin of Mexico is fed from mineral rich aquifers from the surrounding mountain range; with varying mineral concentrations between all the lakes, ranging from freshwater to brackish conditions, depending on elevation, mineral deposits, evaporation, water replacement, and human influences. Out of the original 5 lakes documented in the basin, only Lake Xochimilco and Lake Chalco were classified as freshwater, with low concentrations of salinity. Today, most of the surrounding lake waters have been drained by climate changes and increased water demands, leaving shallow wetlands and marshes behind. Lake Xochimilco is famous for their wetland chinampas, an ancient method of farming on constructed floating islands which have created a network of canals and the last habitat for the few remaining wild axolotls.
Axolotls are currently classified as critically endangered in the wild, with no recent sightings outside of protected refuge areas. Wild axolotls are threatened with rapid habitat loss, heavy environmental pollution, and introduction of invasive predatory fish, carp (Cyprinus carpio) and tilapia (Oreochromis niloticus), which consume eggs and smaller salamanders. There is estimated to be less than a thousand wild axolotls left in their natural environment, though recent reintroduction attempts with captive raised axolotls have had some success in protected canals! The future of wild axolotls will depend on these restored wetlands. Now, this amazing amphibian is thriving in captivity, in estimated millions worldwide!
Unlike most salamander species, axolotls typically do not undergo metamorphosis to lose their gills and live on land. Instead, they retain their water-dwelling larval features for their entire life! This phenomenon of retaining larval features as an adult is known as neoteny, or paedomorphism. However, in very rare instances, it is possible for an axolotl to undergo metamorphosis into a terrestrial salamander. The transition is triggered by a hormone produced by the thyroid, thyroxine, and occurs naturally as the axolotl ages; often before 2 years of age if they are genetically predisposed. Since it's a biological trigger, metamorphosis cannot be caused by stress or unideal water conditions.
In addition to their interesting appearance, axolotls are also known for their ability to regenerate limbs and organs, such as their heart and eye lenses, and even certain parts of their brain! This makes axolotls extremely valuable in medical studies, including cancer research and wound regeneration. Axolotls have long been considered a model animal for scientific research, with some of the first recorded observations and experiments dating back to the 1800s!
Despite their appeal, axolotls have very specific environmental requirements as pets, making them more difficult to care for than some other animals. They require cold, clean fresh water, often requiring a dedicated water chiller, and they are prone to illness and injuries. Their large aquariums require frequent water changes, many axolotls need to be fed directly with tongs, as they're naturally ambush predators that wait in one spot for their meal. Their waste also needs to be removed manually, often with a tool like a cooking baster, as well as manually brushing off algae in the aquarium and siphoning away any debris during routine maintenance. Well-cared for axolotls will have a lifespan of around to 10-15 years commonly, with some reports of 20+ year old individuals.
If you are ready for the responsibility, then this care guide will help you get started on giving your axolotl the best possible home.
Egg
Axolotls begin their journey through life when a female lays hundreds of small, gelatinous eggs.
Over the course of two weeks, the eggs develop into tiny axolotl larvae.
Stages of Life
The average lifespan of an axolotl is approximately 10 years in captivity, however there have been instances of some axolotls living up to 15 years or older. Adult axolotls grow to be 23-30+ cm (9-12+ inches) long on average, reaching their adult measurements around 12-18 months of age. Many factors can influence rate of growth including environmental conditions, diet, age, injury, illness, or genetic factors. Although growth rate slows significantly as axolotls reach maturity, these incredible animals never truly stop the growing process!
Axolotls that do not reach the average adult size are often called "minis". Minis can be as small as 15 cm (6 inches) when fully grown, but still have proportional bodies. This stunted condition can be caused by malnutrition, poor living conditions, or genetic fault.
“Dwarf” axolotls have stunted, disproportional bodies. They can often be identified at a young age by their short, round torso and curvy or bent tail. This deformity is due to genetic influence, and is not considered ethical practice to sell once identified, as it's often a result of closely related genetic parentage. Axolotls impacted with the dwarfism gene will have the same behaviors and needs as any other axolotl; though some specialized care is required to help prevent impaction from over ingestion or accidental substrate inhalation, as they can be more susceptible to organ dysfunction. Dwarf axolotls have an average lifespan of 3-6 years old.
Housing and Tank Requirements
The Aquarium
We recommend 110 liters, or 29 gallons (30" x 12" x 18"/72cm x 30cm x 46cm), per axolotl as the absolute bare minimum aquarium size for axolotls of any size or age. This takes into account both water volume and floor space. However, we strongly recommend getting the largest tank with the most floor space you are able to get; the 180 liter, or "40 gallon breeder style" (36" x 18" x 16"/91cm x 46cm x 40cm), tank is a much more suitable minimum tank size for an axolotl than the 110 liter (29 gallon).
When selecting the aquarium, consider wide and low aquariums over narrow and tall tanks. Axolotls will spend the majority of their time walking around the bottom of the tank, swimming occasionally, and they'll need ample space to explore and be comfortable. Bigger is always better for axolotls and their environments; there is no downside when it comes to increasing walking space and water volume! Larger quantities of water allows for more efficient waste dilution, keeping the water conditions cleaner for longer also less prone to fluctuations in temperature and pH levels over time. Please note that juvenile axolotls grow so rapidly that using a smaller "grow out tank" is often unrealistic for this species.
Axolotls have a very heavy bio load, which means they produce a lot of nitrogen waste as a byproduct of respiration in their environment, resulting in rapid nitrate accumulation. The nitrate level is constantly rising in an established aquarium, and it must be kept below 20 ppm at all times with partial water changes and live plant management in order to not induce stress in axolotls. Performing water changes (~30-70%) on the aquarium is the quickest way to remove any potential pollutants (ammonia, nitrite, nitrate, etc.) and should be done as often as needed to maintain low (<10ppm) nitrate levels, oftentimes weekly or more frequently in smaller aquariums. All live plants will consume small amounts of nitrogen; introducing plenty of plants can help keep the water quality cleaner, as well as provide natural enrichment for the axolotl. Even in heavily planted aquariums, routine water changes are still necessary to reintroduce essential minerals that support pH levels, allow for filter and equipment maintenance, as well as removing other substances that are not detectable with home testing kits, including hormones and potential pathogens.
A sturdy aquarium stand is crucial for safety reasons and preventing household water damages. A safe aquarium stand will be able to fully support all corners and edges of the tank, evenly dispersing the weight of the water and added decorations. Uneven weight distribution puts increased pressure on the silicone sealant and the glass itself, which can cause sudden cracking or compromised seals. The stand should be constructed from a very strong material like steel or thick hardwood planks with proper cross-bracing for optimal stability, since large volumes of water can be extremely heavy. Avoid compressed wood type furniture like inexpensive tables or shelving units as they tend to be made with weaker fibers that are more prone to swelling and bending which can cause instability. Aquarium mats or similar materials can be used between the stand and the tank to help prevent water damage caused by built up condensation or accidental drips.
Another thing to consider is that some axolotls may accidentally jump from their tank if the water level is too high. Jumping can be prevented by keeping the water level a couple inches below the aquarium rim, or by using a lid. Keep in mind that if you are using fans to cool your tank, you will need a breathable lid, such as egg crate/plaskolite covers. A mesh reptile lid, however, will rust over time and leak into the tank.
Aquarium Filters
There are many different types of filters available on the market, and many options can be used in axolotl tanks. When selecting filtration equipment, the most important consideration is adequate filtration power for complete water circulation throughout the whole aquarium. A general rule is at least twice the filter strength to total water volume, for example an 180L/47G aquarium would need filtration rated for at least 360L/94G per hour. Over-filtration is possible as long as the resulting current is not pushing the axolotl against it's will; flows may need to be baffled for juvenile axolotls or very strong filter outputs. This can be accomplished by using a larger filter like a canister unit with an attached spray bar, or using a mix of smaller filters like sponge filters to reach the desired flowrate. Each type of filter has it's own benefits and sometimes drawbacks, ultimately the decision is personal and depends on budget and goals for the habitat!
Filtration equipment styles may differ, but they all follow the basic principals of mechanical filtration, biological filtration, and sometimes chemical filtration methods. Mechanical means to remove physical particles by forcing the water through porous surfaces like sponges and fabric pads. Biological filtration refers to the beneficial bacteria necessary to the nitrogen cycle, and the internal filter media providing ideal surface area for the bacteria to colonize on. Chemical filtration, often pouches of activated carbon, is used as needed to remove medications or other finer impurities from the water column, needing frequent replacement or recharging to maintain effectivity.
Sponge filters are considered the most basic filter option, and are a great budget friendly choice. To operate a sponge filter, an air pump is needed, as well as airline tubing and check valves to prevent accidental siphons. The air pump needs to be rated equally for size of the sponge filter(s) and total aquarium volume. Sponge filters are easy to clean and create a very gentle flow, making them a safe choice for axolotls of any size. Larger sponge filters tend to be bulky which can take up valuable floor space, and some people may consider them unsightly and hard to hide aesthetically. The sponge filter is quiet when in operation, creating gentle bubbles on the surface of the water; the vibration from the air pump on a hard surface is often the loudest noise, putting the air pump on a sponge or plush towel can help dampen the sound.
Internal filters or pond filters are sometimes used, these types of filters are commonly found in aquarium starter kits. The units are attached to a back or side wall of the tank, completely submerged in the water. Internal filters can create a strong flow, so additional spray bars or sponges may need to be purchased to baffle the current. The pump is built in, which creates a hum when in operation. Internal filters can be difficult to customize filter media and to access for cleaning, as most units are constructed to be hard to disassemble.
Hang-on-back type or waterfall filters are considered the next step up from sponge filters, as they don't take up any valuable floorspace and allow for more customized filter media options. These units don't need any additional tubing or pumps to operate, though be aware to avoid cartridge styles that claim to need frequent filter pad replacement! When in use, the filter itself creates a soft hum from the pump, but the resulting splashing can be loud depending on water level of the aquarium, as these units will sit on the top rim of the tank. Some disassembly is required during filter cleaning, making the process slightly more involved, though it is easier to see when the outflow is reduced which is an indicator that maintenance is needed.
Canister filters are often considered to be the most premium filter choice, as they allow for complete filter media customization, don't take up any space inside the tank aside from spray bar tubing, and most importantly can be utilized in-line with aquarium chillers. These units are usually located below the aquarium inside a cabinet, but can be placed almost anywhere beside or lower than the tank; longer or additional hose tubing may be necessary depending on filter model and desired location. Canisters can be easily hidden away, which also muffles any noise from the pump so these units can be very quiet in operation. Cleaning a canister filter is the most involved as they need to be disconnected completely from the tubing hoses and then dissembled layer by layer, eventually reassembled and refilled with water before reconnected to tubing.
All filters will need to be routinely cleaned as a part of ongoing maintenance, most commonly performed during water changes when the filter is disconnected from electricity. Frequency will vary with selected equipment, but should be performed as needed to keep the filter running with optimal outflow, usually every 4-8 weeks, or whenever reduced flow output is observed. Reference the filter instruction manual for specific maintenance instructions. Methods will vary slightly depending on filter style, selected filter media, and personal routine, but there's a few key factors to consider during filter maintenance: Wet bacteria is happy bacteria, avoid letting any filter media dry out completely or using any chlorinated tap water that could potentially disinfect or shock the bacteria with fluctuating temperatures, which could "crash" the nitrogen cycle. Using a separate bucket of aquarium water is ideal for safely rinsing off ceramic or plastic media, and squeezing out sponges to remove debris. Most filter media doesn't need to be replaced until it's disintegrating after several months or years of use, take care to replace filter media slowly as needed and in stages if possible, to avoid discarding significant amounts of beneficial bacteria. Over-cleaning can have detrimental affects on the bacteria cultures as well. To avoid over-cleaning, consider isolating different sections of the filter media if possible and rinsing one section at a time, allowing a few weeks to pass before rinsing a different section. Remember, some mulm/detritus build up is completely expected and a normal part of a healthy ecosystem!
Substrate
There is always an impaction risk when using loose substrate with axolotls because they will always ingest the substrate of the tank. It is important that any gravel, small rocks, and small decorations the size of the axolotl’s head or smaller are avoided. For more in-depth information on substrates, read our article Which Substrate is Safe for Axolotls?
A very soft, fine sand with less than 1 mm grain size poses the least risk for axolotls. Any substrate with particles larger than 2 mm diameter is by definition gravel. When a larger axolotl ingests fine sand, it will usually pass through them without any issue.
However, younger axolotls cannot be kept safely on sand because they are still too small for even fine sand to safely pass through them. We recommend waiting until your axolotl is at least 15 cm (6 inches) long before using a sand substrate.
Some other options are having no substrate at all or using rocks that are significantly larger than the axolotl's head. A bare bottom tank can be easier to keep clean, but may not provide as much grip for your axolotl. If you do not fancy the look of the bare glass, you could even use untreated tiles to dress it up.
Habitat
Providing your axolotl with an enriching and comfortable environment is also important. Putting plenty of hiding spots in your tank is one way to accomplish this. Some axolotls may even interact with bubbles from air stones. Rearranging tank decorations from time to time provides a new layout for your axolotl to explore for enrichment.
Adding live plants is a possibility for an axolotl tanks. However, it should be noted that axolotls do not have eyelids and are sensitive to light. Since low lighting is the most suitable option for axolotls, you will only be able to include plants that can survive in low light cold water, such as Anubias, Elodea, java fern, java moss, Marimo algae balls, and many more.
If you do add aquatic plants to your tank, it is recommended to avoid using any fertilizers. The low maintenance plants that can survive in an axolotl tank typically do not require supplementation, and it is safest to avoid adding extra chemicals to an amphibian tank, since their semi-permeable skin absorbs much more of it than fish would.
Ample hiding spots provide a more comfortable environment for your axolotl.
Marimo balls can be used with axolotls as long as they are larger than the axolotl's head.
Aquatic plants provide a great hangout spot for axolotls.
Some common houseplants, such as pothos and monstera, can be partially submerged in your tank as well, to both help absorb some nitrate and provide hangout spots for your axolotl.
Water Parameters and Temperature
Cycling Your Aquarium
Like all aquatic pets, axolotls require a fully cycled aquarium before they can be added to the tank. It is easiest to refrain from purchasing your axolotl until after your aquarium is fully cycled, as cycling can take 4-8 weeks when done from scratch, without the help of already seeded filter media. Please see our Cycling Guide for a step-by-step walkthrough explaining how to cycle your aquarium through the nitrogen cycle.
Weekly Water Changes
Axolotls are messy, and will quickly pollute their water with their heavy bio-load, leading to increasing levels of nitrate build up in the aquarium. After your tank is fully cycled, it is important to perform weekly, or as often as needed, partial water changes in order to keep the nitrate level below 20 ppm at all times and maintain healthy mineral balance to support pH levels. Ammonia spikes are also common within axolotl tanks, so keeping track of your water parameters with a liquid testing kit is very important. Utilizing live plants in the aquarium is a beneficial way to help maintain lower levels of nitrate accumulation, and provide a more natural habitat for the axolotl.
Water Conditioner
As with any aquarium, a water conditioner must be used when adding any new water to the tank, to ensure there is no chlorine or chloramine that would otherwise damage the beneficial bacteria in the environment, or potential heavy metals that could be a toxin such as lead or copper. Aloe vera is an irritant to axolotls and a common ingredient in many products available in aquatic stores, so make sure that the water conditioner does not contain it before purchasing. Conditioners containing aloe often contain words such as "natural", "plant", "herbal extract", "slime coat", or "stress". The water conditioner should also not contain iodine.
The most commonly recommended water conditioner for axolotls on the market is Seachem Prime, or Seachem Safe as it is axolotl-safe and has other added benefits such as cost efficiency. Seachem has recently released their own branded Axolotl Conditioner, which is just their Prime solution rebranded, so it is a safe option but be aware the cost may be more expensive to capitalize on market trends. Some other axolotl safe water dechlorinators are Aqueon Water Conditioner, API Aqua Essential, though be cautious that API Stress Coat and many other alternatives contain aloe vera and therefore are not a compatible option with axolotls.
Water Quality
Axolotls are heavily influenced by the water they inhabit, which directly affects their overall health. It is essential to be able to test the water in the aquarium as well your own source or tap water; testing the water in the aquarium weekly or whenever unusual behavior in the axolotl is observed.
Tap water quality can vary greatly depending on region, urban utilities, and environmental influence, so it's essential to gather as much information possible about your individual source water! Detailed water reports are often available online for cities and towns with water treatment systems. Ground wells are recommended to be tested yearly at minimum. Home fresh water testing kits are available to purchase, with liquid or digital testing being considered the most accurate and recommended for axolotl keepers. Additionally, paper strip tests are available, but tend to provide less accurate results. Every test kit brand will have differing instructions, so it's important to read and perform each unique test exactly as stated for the most correct results.
Ideal tap water parameters are 0ppm ammonia, 0ppm nitrites, <5ppm nitrates, and pH between 7.2-8.4 for axolotl aquariums.
Temperature is ideal between: 12-20˚C (53.6-68˚F)
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Maintaining a cool water temperature is essential because axolotls are an ectothermic species, meaning they rely on their environmental conditions to regulate their bodily functions including metabolism and respiration. Temperatures higher than 20°C (68˚F) will quickly lead to stress, lowering natural immunity, which can make axolotls more susceptible to opportunistic diseases and infection. Increased water temperature raises metabolic rate and lowers available oxygen in the environment, leading to increased passive energy consumption as their systems work harder to maintain equilibrium. Over 22°C (71.6°F) for extended periods will be stressful and suppressing immune response, while over 24°C (75.2°F) can be fatal. On the other hand, temperatures lower than 10˚C (50˚F) will begin to slow metabolism significantly, which is detrimental for long periods of time as they may struggle with full nutrient absorption or possible Gastrointestinal Overload (GIO) syndrome. It is very important to have a consistent means of keeping your axolotl’s tank within a comfortable range. See our article How to Lower the Temperature in an Axolotl Tank for more information.
Ammonia (NH₃/NH₄⁺) is ideal between: 0-0.25ppm
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Ammonia or ammonium is the main waste byproduct found in water systems, as it's created naturally with aquatic animal respiration and waste production, as well as from any decaying organic matter. Ammonia is a toxic compound, and can burn the gills and skin of axolotls in elevated concentrations, above 0.5ppm exposure can cause irritation, stress, or even death in severe circumstances. In a fully cycled aquarium, ammonia will be at 0ppm as the nitrifying bacteria is continually working to break down the waste that being created passively. Ammonia spikes can happen unexpectedly, most often a result of hidden accumulated waste or the nitrosomonas culture was damaged accidentally. If there is elevated ammonia levels in the aquarium, perform a large (50-75%) water change right away and continue to monitor parameters daily to ensure the nitrogen cycle is intact. For more information on how to cycle your tank, please see our Cycling Guide.
Nitrite (NO₂⁻) is ideal at: 0ppm
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In a fully established aquarium, nitrite will be at 0ppm at all times. Nitrite is a highly toxic byproduct of the nitrogen cycle, which forms when ammonia becomes "fixed" by the nitrosomonas bacteria with oxygen ions. Nitrobacter cultures will "fix" nitrite further with additional oxygen ions, finally resulting in nitrate formation. Elevated levels of nitrite can suffocate and poison all aquatic life, and can be fatal in axolotls with prolonged exposure over 0.25ppm. It is essential nitrite stays at undetectable levels once the aquarium is inhabited. If there is any detectable nitrite in the aquarium, consider tubbing the axolotl to minimize toxin exposure while waiting for the beneficial bacteria to reestablish. For more information on how to cycle your tank, please see our Cycling Guide.
Nitrates (NO₃⁻) is ideal between: 5-20ppm
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Nitrate is the final stage of the nitrogen cycle as ammonia is broken down, and is continually increasing in an established or cycled environment. Nitrate is the least toxic state of nitrogen, though is still considered toxic in high concentrations for axolotls over 20ppm. Elevated levels of nitrate over time can cause gill filament deterioration, poor slime coat formation, decreased appetite and metabolism, cloudy eyes, and weakened immune functions. Even though nitrate should always be kept below 20 ppm with routine water changes and live plants, a reading of 0ppm can indicate the aquarium is not cycled. Low nitrate results is common in aquariums that have a significant amount of live plants to combat nitrate production, or the aquarium water was very recently replaced. Incorrect testing results from improperly performed tests or expired kits will also show lower values than expected. Elevated nitrate levels above 20ppm can be managed quickly with a large water change as necessary, as long as the new water being added to the aquarium doesn't contain any ammonia, nitrites, or nitrates.
Power/Potential of Hydrogen (pH) is ideal between: 7.2-8.4
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pH measures the amount of hydrogen (H+) ions found in the water, which indicates how acidic, neutral, or alkaline the parameters are. The pH scale ranges from 0-14 on a logarithmic scale, with 0-6.8 pH being acidic conditions, 7 pH neutral, and 7.2-14 pH being alkaline (basic) conditions. The pH in water is influenced by many factors including, alkalinity, oxygen, temperature, organic waste and pollutants. A stable and slightly alkaline pH is essential for overall environmental quality, as it influences many biological functions within the aquarium such as nitrifying bacteria production, ammonia and nitrite toxicity rate, plant cell stability, and directly affects the slime coat, tissues, and skeletal systems in axolotls. Rapid changes in pH can be detrimental, as it can alter cell structures with fluctuating ionic density, which can result in cell death and tissue damages, leading to stress and potentially fatal consequence. Although pH will naturally shift throughout the day in heavily planted aquariums with the photosynthesis cycle, it is essential to keep pH levels as consistent as possible, changing by no more than 0.2 value in 24 hours with manual adjustment methods. A consistent pH is key to maintaining a healthy environment!
Carbonate Hardness (KH) or Alkalinity is ideal between: 3-7˚ (53.7-125.3 ppm)
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KH measures the pH buffering capacity of the water, or the water's capacity to resist changes in pH when exposed to acidic compounds. Alkalinity is essential to stabilize pH levels in water, and provide essential nutrients for all cellular life, as KH is composed mostly of bicarbonates (HCO₃⁻), carbonates ( CO₃²⁻), and hydroxide (OH−) ions. The more alkalinity that is present in the water, the more stable the pH level stays over time in an aquarium, often around 8pH. Low levels alkalinity can be supplemented with measured dosages of alkaline buffers or sodium bicarbonate/plain baking soda. Packaged additives need to be utilized every time new water is being added to the aquarium, to keep mineral levels consistent, if the source water is lacking or when using primarily processed water such as RO/DI (Reverse Osmosis/Deionized), or distilled. Powdered or crystalized additives need to be dissolved completely in a separate container of dechlorinated water before being added to the aquarium. Alkalinity can also be increased passively by using calcium carbonate based items within the aquarium such as crushed coral/shells or aragonite within a mesh media bag, or large limestone rock pieces, which dissolve slowly in the water column over weeks before replacing as needed. Once the water has become saturated with carbonates, the dissolution process plateaus naturally, using only as much as needed to maintain equilibrium until eventually depleted.
General Hardness (GH) is ideal between 7-14˚ (125.3-250.6 ppm)
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GH is a measurement of calcium (Ca²⁺), magnesium (Mg²⁺), and potassium (K+) found in water, often expressed in mg/L or parts per million then converted to degrees of hardness. The General Hardness range can vary depending on country and units of measurement being used, but most commonly 0-3˚dH (0-60ppm) is considered soft water, 4-8˚dH (61-160ppm) being moderately hard water, 9-14˚dH (161-250ppm) is hard water, and above 15˚dH (251ppm+) is very hard water. Axolotls need mineral rich hard water to support overall health including bone density, tissue development, osmoregulation and innate biological functions. Source water that is low in GH can be supplemented manually with mineral additives like chloride salt blends including Seachem Replenish, Seachem Equilibrium, or modified Holtfreter's solution. Alternatively, passive methods with crushed coral/shells or aragonite within a mesh media bag in the waterflow will raise GH levels as it dissolves gradually. Axolotls can adapt to very hard water conditions without detriment, though excessive GH levels can result in frequent mineral build up on equipment.
Salinity is ideal between: 0.6-1ppt
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Salinity is a measurement of the total dissolved salts present in the water, commonly written in parts per thousand (ppt) or as a percentage to water volume, which mostly is influenced by sodium chloride (NaCl) levels. Axolotls originated from freshwater saline lakes with ranging salt and mineral concentrations, and research commonly supports that axolotls benefit overall with trace levels of sodium chloride, also non-iodized table salt or rock salt, in their environment to help with osmoregulation and essential electrolyte transmission to support development and neurological functions. Aquarium salt or other similar salts can be used in measured amounts to increase salinity as long as they do not contain iodine or any other anti-caking agents, and must be dissolved completely and separately before adding to the aquarium or tub. One tablespoon of salt per ~19L/5G of water will raise the salinity to ~0.8ppt in the aquarium. Elevated salinity levels over 2.2ppt can be very damaging or even fatal in axolotls with prolonged exposure. It is essential to only add aquarium salt for the water being replaced in the aquarium, not evaporated passively, as salts and minerals will stay in the water indefinitely. Isolated salt baths up to 15g/L can be tolerated for brief 10-30 minute treatments for some diseases.
Test Your Water Frequently!
The well-being of animals cannot be judged only by looking at them.
The only real way to know if your axolotl is stressed is by always knowing your water parameters.
Water can easily become toxic if not monitored closely.
Diet
Staple Foods
Axolotls require earthworms or night crawlers in order to have proper nutrition. Earthworms and night crawlers meet the nutritional requirements of your axolotl better than any other option, as they contain over 60% protein and a Ca:P ratio greater than 1.
On top of that, they are typically easy to find in bait shops, pet stores, or online in bulk. Starting a worm farm may be a beneficial investment for supplying your axolotl with food.
To supplement the axolotl's main diet of worms, axolotl pellets are one of the foods that may also be fed. There are several axolotl-specific pellets available. If you are unable to find axolotl pellets, then sinking carnivore pellets can be used. Read our Axolotl Nutrition article for in depth information on different food options and their nutritional value.
Treats
If you are looking to treat your axolotl, you may offer occasional treats, like waxworms, frozen brine shrimp or bloodworms, Repashy Grub Pie, and blackworms. Keep in mind that these foods are classified as occasional treats, due to not being as nutritionally complete as earthworms.
Live cherry or ghost shrimp tank mates are also an option for your axolotl to snack on. However, if you choose to keep shrimp with your axolotl, it is safest to breed your own, or at the very least quarantine and medicate any that you purchase from pet stores for at least 30 days to screen for diseases and parasites before introducing them to your axolotl’s tank.
Do Not Feed
Feeder fish such as goldfish and minnows contain thiaminase, which will cause a thiamine deficiency in your axolotl when they are eaten consistently. Other fish tend to nip at and damage the axolotl's gills and slime coat, and fish from pet stores will also easily spread diseases and parasites. In addition, many fish have different temperature requirements than axolotls and cannot be housed comfortably in cold water.
Most insects should not be offered to axolotls. Insects and their larvae often contain chitin, which is indigestible to axolotls. Insects also do not fulfill the dietary requirements of axolotls.
Behavior
General
Axolotls will generally sit around their tank all day. They are opportunistic hunters that will stay in the same area waiting for prey to pass by instead of actively searching for it. You may also see your axolotl walking along the bottom of the tank as well as occasionally swimming around.
Fired Up
Axolotls may even “fire up” at times. When this happens, axolotls may take on a lighter color and their gills become more red for a brief period of time, due to increased blood flow. Axolotls may be more active or eating when this occurs. This is completely normal and nothing to be concerned about.
Abnormal Behavior
Some behaviors may be indicators of stress or illness. These include forward curled gills, swimming erratically, writhing, loss of appetite, frequent uncontrolled floating, scratching at their gills with their back leg, or a fold in the very tip of their tail. If your axolotl exhibits any of these behaviors, test your water parameters right away.
Determining Sex
While axolotls typically cannot be definitively sexed until they are around 12-18 months old, there is no set age within this range to determine the sex of an axolotl, as every axolotl develops at a different rate. Please read our How to Determine the Sex of an Axolotl article for more detailed information.
Males
The average age to identify a male is around 12 months, but they can be identified as early as 5 months or as late as 18 months depending on when they develop an enlarged cloaca. In uncommon cases, an axolotl can be identified as a male as early as 5 months if the cloaca is already becoming visibly enlarged, but they can also be late bloomers and take as long as 18 months to present an enlarged cloaca.
A male cloaca is visible as a protruding bump behind its back legs. Male axolotls will typically have slimmer body shapes with longer tails. One way to differentiate male and female cloacas is to note that a male cloaca bulges from the sides.
Females
While the males have a very obvious sign of their sex, female indicators are much less definitive. Female axolotls are typically more plump than males and may have a shorter tail. A female axolotl cannot be identified with 100% certainty until it is around 18 months old, as even a plump, short-tailed axolotl could turn out to be a male.
Tank Mates
As with all aquatic animals, make sure that if you do decide to get your axolotl a tank mate to quarantine them for at least 30 days to screen for parasites and diseases before introducing them to the tank. Some parasites may take even longer than 30 days to become apparent. For a more in-depth information on tank mates, read our article Can Axolotls Have Tank Mates?
Other Axolotls
Unfortunately, axolotls generally do not do well with tank mates. The safest tank mates that you can keep with your axolotl are small shrimp.
Although they may often invade each other's personal space, axolotls are not social animals. They are a solitary species that does not care either way whether they are housed with another member of their species, and they feel no sense of company nor loneliness.
There are no benefits to cohabiting axolotls, and the situation is neutral at best. Keeping more than one axolotl in the same enclosure poses danger, as they easily mistake each other for food, may mate and produce accidental eggs, and more than one axolotl in a small aquarium will cause nitrate levels to rise quickly.
Risk of Injury
Axolotls often mistake one another for food and will bite each other. If axolotls are housed together, they must be fed far away from each other in the tank to avoid injury. Once the axolotl sees its owner, it will begin to equate anything moving nearby with food, which easily results in nipping. They must also be fed frequently enough to avoid nipping in general. Axolotls can easily eat each other if size difference allows one's head to fit inside the other's mouth.
Accidental Breeding
If juvenile axolotls are housed together, there is a high probability that they will turn out to be opposite sex. If a male and a female are together, then they will breed. If you are not intending to breed, then you will end up with hundreds of accidental eggs scattered throughout your tank.
It is very important to remember that eggs from parents with undocumented genetic history and lineages should never be raised. If your axolotls have accidentally bred, the eggs should be culled humanely by freezing in order to prevent more harmful and unknown genes from being spread.
The population of captive axolotls is currently suffering from various genetic issues, so it is imperative that we only ever breed axolotls from ethical breeders with tracked genetics and lineages. It should also be noted that female axolotls should not be bred more than once every 6 months. Overbreeding is stressful to female axolotls, and may make them more susceptible to diseases.
Shrimp
Some owners may use ghost (Palaemon paludosus) or cherry (Neocaridina davidi) shrimp for detritus cleanup in their axolotl tank, but they will most likely get eaten by the axolotl. It is recommended to not add shrimp to your axolotl tank until your axolotl is at least 15 cm (6 inches) long to ensure that the axolotl can swallow them safely. It is also recommended to quarantine any new additions for 30+ days, to monitor for potential parasites or disease, before introducing to an established ecosystem. In some cases, axolotl keepers will have additional aquariums for shrimp breeding!
Sources
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Merck Veterinary Manual. (n.d.). Infectious diseases of amphibians. https://www.merckvetmanual.com/exotic-and-laboratory-animals/amphibians/infectious-diseases-of-amphibians
LafeberVet. (n.d.). Basic information sheet: Axolotl. https://lafeber.com/vet/basic-information-sheet-axolotl/
Veterinary Information Network (VIN). (n.d.). Common disease conditions in axolotls. https://www.vin.com/apputil/content/defaultadv1.aspx?id=7259254&pid=14365
Safari Veterinary Care Centers. (n.d.). Care of the axolotl. https://www.safarivet.com/care-topics/reptiles-and-amphibians/care-of-the-axolotl/?amp
Walker, L., & Jiang, A. (n.d.). Dechlorination and nitrogen cycling at Georgia Aquarium for fresh and saltwater exhibits. ResearchGate. https://www.researchgate.net/profile/Latosha-Walker/publication/337307074_Dechlorination_and_nitrogen_cycling_at_Georgia_Aquarium_for_fresh_and_saltwater_exhibits/links/5f46e85f299bf13c50390ea9/Dechlorination-and-nitrogen-cycling-at-Georgia-Aquarium-for-fresh-and-saltwater-exhibits.pdf
Veterinary Information Network (VIN). (n.d.). Water quality explained: How it can affect your axolotl's health. https://www.vin.com/apputil/content/defaultadv1.aspx?id=7259211&pid=14365&print=1
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