Is a fungal infection on an axolotl an emergency?

Not usually, if it's caught early and small — but it can spread quickly on gills specifically, which are vital tissue. Treat the water immediately and watch closely rather than waiting.

Can I use regular aquarium salt on an axolotl?

Only briefly and dilute, as a bath rather than a permanent tank additive. Axolotls have permeable skin and are more sensitive to salt than most fish; if you're not confident on dosing, skip it and focus on water quality plus a vet consult.

Urgent

White fuzzy or cottony patches

This looks like: a fungal infection (most likely Saprolegnia), almost always secondary to a water-quality problem or an injury

Do this firstTest ammonia, nitrite, and temperature immediately — fungus this visible is almost always riding on an underlying water problem, and treating the fungus alone won't fix that.

Why this happens

Saprolegnia is a waterborne fungus that's present in most tanks at low levels and only takes hold on tissue that's already damaged, stressed, or immune-compromised — usually from ammonia/nitrite exposure, a temperature spike, or a physical injury. The fungus itself is rarely the root cause; the water or the wound underneath it is.

How sure are we? Fluffy white/grey cottony growth is a fairly distinctive fungal pattern, but bacterial infections can look similar on gills specifically — test water and look closely before treating.

What to do right now

Test ammonia, nitrite, and temperature immediately — fungus this visible is almost always riding on an underlying water problem, and treating the fungus alone won't fix that.
Do a water change and correct whatever's off. If temperature is high, cooling it is part of the treatment, not a separate task.
If you want to treat the patch directly, a brief (10-15 minute), dilute aquarium-salt bath is a widely used axolotl-specific approach — but axolotls are far more sensitive to salt than fish, so get the concentration right or skip it and go straight to the next step.
Move to a bare-bottom hospital tank if you have other axolotls or fish, so you can monitor closely and control the water precisely.
If the patch spreads past a small area, reaches the gills significantly, or doesn't improve in 2-3 days, see an exotic/aquatic vet — prescription antifungals exist and are worth it once home measures stall.

What not to do

Don't reach for standard fish antifungal medications without checking axolotl safety first — many contain malachite green or copper, both toxic to amphibians through their skin.
Don't scrub, pick at, or net-drag the patch — you'll strip more slime coat and open more sites for infection.

Stop it happening again

Keep water quality stable and treat injuries promptly - fungus almost always follows stress or an open wound, so preventing those prevents this.

If that doesn't fix it

If it keeps coming back even with clean, stable water, the fungus is a symptom of something chronic — check for a slow ammonia creep, an old unhealed injury, or overcrowding stress, and consider a vet visit to rule those out properly.

Catch this earlier next time — log your axolotl's water parameters in App-aquatic. Free forever.

This isn't veterinary advice - it's a directional read to help you decide your next step, based on the most common causes and independently checked sources (Merck Veterinary Manual, PetMD, established amphibian husbandry references). We can't see your axolotl, so pair it with a liquid test kit and clear photos, and see an exotic or aquatic vet for anything serious or not improving.