Fungus can appear on axolotls for various reasons like stress or warm temperature, so it can happen anytime.
Most common place for fungus to appear are your axolotl's gills, you'll spot a fluffy white ball. If you see that, you want to tub your axolotl in cool dechlorinated water preferably with an Indian Almond Leaf. The tannin of the IAL will help your axolotl.
(You can also use IAL for an injury, if your axie slime coat is peeling off, anything to improve his skin.)
You can try to gently remove the white fluffy fungus with a cotton bud. It won't work all the time though.
After tubbing your axolotl with an IAL if the fluff still remain I recommend to do a Tea Bath.
It's the most gentle and efficient treatment for fungus.
I hear people doing salt bath for fungus but salt bath are really really harsh on axolotls skin so I personally don't recommend it for a simple case of fungus.
Let your axolotl tubbed until the fluff is gone. If spotted early it can last only a few days.
