Axolotl bacterial infections

The #1 Biggest Killer of Axolotls Each Year?

The #1 Biggest Killer of Axolotls Each Year?

There's something sinister lurking in every axolotl aquarium...

... And it's something that gets very easily overlooked.

Keep reading to find out.

The Truth About Bacteria


Your water parameters can be perfect.

Your temperature can be perfect.

But your axolotl can still be sick with no obvious cause.

Sometimes the axolotl can sicken and die with equal speed, seemingly out of the blue.


There are several reasons, but the biggest one is probably...


Bacterial infections claim the lives of countless axolotls every year.

There are many types of bacteria in the water.

Some are good, some not so much.

The not-so-much ones I referred to may be harmless under the right conditions, provided they exist:

  • In low numbers
  • In the presence of a competent immune system of a healthy animal
  • In the absence of injury or other stressors such as poor water quality and overcrowding
  • In the presence of a good, solid aquarium environmental microbiome

But reverse the cases above, and they can become very dangerous to your pet.

(And some kinds can be dangerous in low numbers even with all the above.)

For example:

Your water can be crystal clear with perfect parameters.

But high bacterial counts in the water can cause problems for your axolotl through something pathologists call dose response.


In low numbers, certain kinds of bacteria can present problems depending on the exact species of bacteria you are dealing with, which can vary from tank to tank.

Some bacteria strains are very bad.

M. marinum for example are very dangerous and can decimate entire tanks.

Another example?

Aeromonas hydrophila, commonly known as "red leg" or "septicemia" can be introduced through contamination of the water.

But there are bacteria that exist in ALL aquariums that can cause disease.

They don't always come as a result of contamination.

And as stated, in low enough numbers, and with a healthy animal, they generally don't cause issues.

But if any one factor is off, they can.

And here's the bad news:

Bacteria in general are FAR more dangerous to your axolotl even than the dreaded fungus.

Because of their prevalence, in some lab axolotl colonies, yearly antibiotic injections are administered to prevent disease.

We don't agree with this approach at Fantaxies, and prefer to use the methods below to keep our animals free from bad bacteria problems.

What Can You Do?


Now you know there is a threat lurking in your tank.

What can you do about it?

1. Add a UV Sterilizer

UV sterilization is a fantastic way to combat high bacteria counts in the water, killing harmful bacteria that can cause disease.

In the wild, the UV in natural sunlight does some of this already.


In captivity, most aquariums do not receive any direct sunlight.

We can help compensate in an artificial environment by adding UV sterilization technology to our aquariums.

The exact brand isn't as important as its ability to kill suspended green algae.

UV sterilizers can combat the bacteria counts in aquarium water that, when built up to high numbers, can suppress the immune system of the axolotl and lead to disease.

There are several types available, that all accomplish the same end goal.

The water just needs to be flowing through it and have contact with the UV light inside the unit.

Some can be connected to an external filter, such as a canister filter, but I prefer the kind that are their own individual units.

You can pop one of these in the tank by suctioning it to the glass, turn it on and the water pumps through.

The brand we use here at Fantaxies is Green Killing Machine, and it comes in different sizes depending on how big your tank is:


If your tank is in between sizes, I recommend sizing down.

So for example:

For a 75 gallon, you will want a 9 Watt sterilizer.

This is because the flow rate, if you size up, can stress the axolotl.

They don't do well with much current (and neither do most aquarium plants).


Please note that a UV sterilizer is generally not strong enough to harm parasites and break their life cycle, and is not a treatment for an axolotl with an active fungal infection.

It should be considered a preventative measure in a multi-pronged approach to keep your axolotl healthy.

2. Axie Aid

The active ingredient in Axie Aid reduces the number of suspended bacteria and bacteria on surfaces in the tank as well.

This can be useful in the case where there is a pathogen entrenched in the aquarium itself, especially in the case of parasitic diseases and some cases of fungus.

If your axolotl is already sick with an external infection of some kind, we recommend considering Axie Aid to kill the pathogens on that animal so the immune system can rebound.

It can be used in the aquarium directly, however, remember to bypass the filter so you don't lose your good bacteria.

Afterwards, once your aquarium has been set up in a way to minimize fungal outbreaks in the tank itself, we would recommend using it as needed in a hospital tub or tank.

Which brings us to our next point...

3. Solid Aquarium Environmental Engineering

Believe it or not?

Generally speaking...

A healthy aquarium = a healthy axolotl.

How you set up your tank can actually make a big difference in how often you are dealing with problems like fungus and external bacterial infections.

(This comes back to a good, solid environmental microbiome in your aquarium as a measure to prevent disease touched on earlier.)

It sounds counterintuitive, but tanks that are too sterile actually lend themselves to the fostering of bad bacteria.

Because the good bacteria lacks enough space to colonize in most aquariums, bad bacteria tend to get the upper hand in the environment.

A filter has good bacteria, yes, but these are mostly nitrifying bacteria and their purpose is not to keep bad bacteria numbers in check, but rather the water parameters.

If you have issues with disease in your axolotls, we recommend asking yourself the following questions:

  • Does your tank have an abundance of healthy, growing live plants, or is the decor mostly non-living?
  • Does your tank have a competent system for nutrient recycling and breaking down organic waste, or are you relying on water changes for this?
  • Does your tank have a neutral smell, or an unpleasant one?
  • Does your tank have deep substrate for promoting the colonizing of aerobic and anaerobic bacteria, or are you using a thin layer of substrate for cosmetic purposes?
  • Does your tank have a system in place for mulm diffusion?
  • Does your tank have a filter that doesn't create a strong flow?

The items in bold are all indications of an aquarium that lends itself to a healthy axolotl.

4. Water Changes

Lacking the above methods of promoting healthy bacteria and removing bad ones, the aquarist generally must resort to water changes to reduce high bacterial counts in the water.

The disadvantages of this are primarily due to increased work load...

But frequent water changes may also be a potential cause of mild stress to the axolotl, especially if the original water is quite a bit different than the new water.

However, in the case of tubbing sans filtration, it is usually required to maintain clean water in a small environment.


Generally speaking...

Prevention is far better than treatment.

We hope the tips above help your pet live their healthiest life possible!


Reading next

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Why Isn't My Axolotl Eating? 9 Causes (& What to Do)

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