Can I keep an axolotl with fish in the same aquarium?

It is strongly discouraged. Fish live at temperatures higher than the axolotl tolerates, so temperature alone is incompatible. On top of that, many fish nip the axolotl's external gills, which are delicate and slow, while small fish risk being swallowed and can carry parasites. The axolotl does best alone or, at most, with another axolotl of similar size in an adequate volume, avoiding markedly different sizes that might bite one another.

What substrate should I put in an axolotl tank?

Fine aquarium sand or no substrate at all, meaning bare glass. The reason is safety: the axolotl catches food by suction, and it sucks in whatever is around it too. With gravel or small stones it risks swallowing grains it cannot pass, causing an intestinal blockage, one of the most serious and common problems in the species. Fine sand, if swallowed, is usually passed; gravel is not. If in doubt, bare glass is the safest choice for juveniles.

The water gets too warm in summer: how do I cool it?

Temperature is the critical parameter, so summer heat needs a plan. The solutions, in rising order of effort, are: keep the tank in the coolest room and away from sun facing windows, use fans blowing across the surface to cool by evaporation, reduce the lighting, and in very hot climates fit an aquarium chiller. Avoid abrupt changes with iced water, because a rapid swing stresses the animal as much as the heat itself.

How often should I change the water and test the values?

A weekly partial water change is a good starting rule for a single adult in a cycled tank, with treated water at the same temperature. Test the values regularly, more often in the first weeks after introduction and whenever you notice a change in the animal, such as loss of appetite or gills that look different. The aim is to keep ammonia and nitrite at zero and nitrate low: if they rise, increase the frequency of changes rather than waiting.

Non conventional species55 minLevel: IntermediateUpdated on August 20, 2026

Setting up and running an axolotl aquarium

How to set up an axolotl tank: cool water, the nitrogen cycle, a safe substrate, gentle filtration and feeding, with the water values you need to keep.

Audience: Pet owners
Species: All species
Scope: Valid everywhere, Italy, European Union

What you need before you start

Un acquario di almeno 80 litri per un singolo esemplare adulto
Un test dell'acqua per ammoniaca, nitriti e nitrati, non le sole strisce colorate
Un termometro affidabile e, nei climi caldi, un modo per tenere l'acqua fresca

The axolotl is often bought as if it were a colourful fish, and almost every mistake springs from that misunderstanding. It is not a fish, it is an amphibian that stays aquatic its whole life, with needs largely opposite to the tropical tanks you see in shops: it wants cool water rather than heated, weak flow rather than turbulence, low light rather than a bright lamp. Get those three wrong and the animal, which can live well over ten years, falls ill within weeks. The good news is that, once you understand its rules, the axolotl is among the easiest aquatic animals to keep. This guide explains how to set the tank up from day one, with the caveat that a sick individual needs a vet experienced in exotics.

Why an axolotl is not a tropical fish

Before buying any equipment it helps to fix three differences that turn the setup on its head compared with a classic aquarium. The axolotl is a cool water animal, delicate skinned and scaleless, and it lives resting on the bottom, not in the water column. Everything follows from that: no heater, flow cut to a minimum and a substrate chosen so as not to harm it. Anyone starting from a ready made tropical tank tends to make the same mistakes.

It wants cool water: heat is the first cause of stress and illness, not cold.
It has bare skin and fragile external gills that strong flow irritates and wears down.
It lives on the bottom, so substrate choice is a safety matter, not decoration.
It prefers dim light: a bright lamp makes it uneasy and serves no purpose.
It does not live with fish, which stress it, nip its gills or get swallowed.

The tank, the substrate and the flow

The physical setup decides much of the animal's future health. Three choices matter more than the rest: tank size, which must give space and water stability; substrate, the most common cause of digestive trouble; and filtration, which must clean without creating flow. Better to spend well here than to chase problems later.

Choose a wide, low tank
For a single adult start from at least 80 litres, ideally with more footprint than height. A larger volume holds temperature and values steadier, and the axolotl uses the floor, not the depth.
Decide the substrate: fine sand or none
Use fine aquarium sand or leave the glass bare. Avoid gravel and small stones: the axolotl sucks in its food and any grains with it, which can cause an intestinal blockage, among the most serious and frequent problems.
Fit a low flow filter
You need a filter to maintain the nitrogen cycle, but the flow must stay weak. Aim the outlet at a pane of glass or use a baffle, so the gills are not always under a current.
Add hides and shaded areas
A cave, a root or a broad leaf gives the animal a refuge and lowers stress. Dim light is a requirement, not a decorative whim.
Skip the heater
Do not fit a heater. If the home is warm, think instead about surface fans, a cool room or a small chiller, according to the climate you live in.

Cycle the water before arrival

The step almost everyone skips is also the one that saves the most axolotls: cycling the tank before the animal goes in. Cycling means growing in the filter the bacteria that turn ammonia, which is very toxic, into nitrite and then into nitrate, which is less dangerous. In an uncycled tank the ammonia the animal produces builds up and poisons it within days. The cycle takes weeks, so you start it well before you buy.

Fill the tank with water treated with a dechlorinator, which neutralises chlorine and chloramine.
Start the filter and add a source of ammonia to feed the bacteria, following a controlled cycling method.
Measure ammonia, nitrite and nitrate with a reagent test, more reliable than strips alone.
Wait for ammonia and nitrite to return to zero and nitrate to appear: the sign the cycle is complete.
Do a partial water change to lower nitrate before introducing the animal.
Add the axolotl only once the values stay stable, not as soon as the tank looks ready.

The water values to keep

The axolotl forgives many mistakes except those about the water. Keeping a few parameters in check, with regular water changes, prevents most illnesses. The table sums up the ranges commonly used for a healthy animal: they are practical references, not a prescription, and should be adapted to the individual tank.

Indicative values for a healthy adult axolotl. For a sick animal or specific doubts, the reference remains a vet experienced with amphibians.
Parameter	Indicative range	Note
Temperature	16-18 degrees	Prolonged heat is dangerous, keep it cool and stable
Ammonia	0	Any value above zero is toxic and must be corrected at once
Nitrite	0	Like ammonia, it signals an incomplete or failing cycle
Nitrate	Below 20-40 mg/l	Lowered by regular water changes
pH	7.4-7.6	It prefers water from neutral to slightly basic
Flow	Weak	Still, open gills indicate an adequate flow

Feeding and weekly maintenance

Once the tank is set up well, daily management is simple and comes down to two things: giving the right food without fouling the water and holding the values with regular changes. Consistency counts more than the amount of work: a few repeated actions beat one big occasional clean.

Offer suitable foods such as earthworms, sinking species specific pellets and small invertebrates, avoiding prey that is too large.
Set the frequency by age: juveniles eat more often, adults every two or three days.
Remove uneaten food promptly, because in cool water it decays and raises ammonia.
Do a partial water change each week with treated water at the same temperature as the tank.
Gently vacuum the bottom to remove faeces and debris, without dismantling everything and without washing the filter under tap water.
Record temperature and values after each test, so you catch a bad trend early before it becomes a problem.

Frequently asked questions

Can I keep an axolotl with fish in the same aquarium?: It is strongly discouraged. Fish live at temperatures higher than the axolotl tolerates, so temperature alone is incompatible. On top of that, many fish nip the axolotl's external gills, which are delicate and slow, while small fish risk being swallowed and can carry parasites. The axolotl does best alone or, at most, with another axolotl of similar size in an adequate volume, avoiding markedly different sizes that might bite one another.
What substrate should I put in an axolotl tank?: Fine aquarium sand or no substrate at all, meaning bare glass. The reason is safety: the axolotl catches food by suction, and it sucks in whatever is around it too. With gravel or small stones it risks swallowing grains it cannot pass, causing an intestinal blockage, one of the most serious and common problems in the species. Fine sand, if swallowed, is usually passed; gravel is not. If in doubt, bare glass is the safest choice for juveniles.
The water gets too warm in summer: how do I cool it?: Temperature is the critical parameter, so summer heat needs a plan. The solutions, in rising order of effort, are: keep the tank in the coolest room and away from sun facing windows, use fans blowing across the surface to cool by evaporation, reduce the lighting, and in very hot climates fit an aquarium chiller. Avoid abrupt changes with iced water, because a rapid swing stresses the animal as much as the heat itself.
How often should I change the water and test the values?: A weekly partial water change is a good starting rule for a single adult in a cycled tank, with treated water at the same temperature. Test the values regularly, more often in the first weeks after introduction and whenever you notice a change in the animal, such as loss of appetite or gills that look different. The aim is to keep ammonia and nitrite at zero and nitrate low: if they rise, increase the frequency of changes rather than waiting.

What to do next

Treat the axolotl for what it is, a cool water amphibian and not a fish: a wide tank of at least 80 litres, a substrate of fine sand only or bare glass, a low flow filter and no heater. Cycle the tank before arrival, keep the temperature cool and ammonia and nitrite at zero, feed earthworms and sinking pellets, and do a weekly partial water change while logging values and appetite. For a sick animal, turn to a vet experienced with exotics.