Neon With White Mark On Mouth

There are a couple of possibilities.

It could be that it has cut its mouth and you are seeing scar tissue, the fish equivalent of a scab. You often see this in fins when fish have been fighting, it is inside the fin rather than on the surface like whitespot.

It could be the start of mouthrot. This is a bacterial infection, treated with medication such as Myxazin by Waterlife or eSHa 2000 (they are the best ones, though not all shops stock them). Keep an eye on for a couple of days. if it is physical damage it will clear up. But if it doesn't or shows signs of getting worse, use a medication. Take out any carbon or carbon sponges in your filter, then run some new carbon to get rid of the med once treatment has finished. I can't remember if you have shrimps or snails - you would need to remove them for the duration.


To set your mind at rest in case you have come across mention of it, this is not one of the symptoms or neon tetra disease.