Sick fish?

[Anna94]

What is this spot on my fish?

 

[Toad]

Hard to tell, maybe columnaris? How long has it been like that? Any other fish showing signs?

 

[flitabout]

Something is definitely wrong. I can rule neon tetra disease because they are cardinals. It doesn't look like columnaris either the spot is to dark or at least it appears that way in the picture.

 

[Anna94]

Hard to tell, maybe columnaris? How long has it been like that? Any other fish showing signs?

Just the one fish.

 

[V227]

Might be an injury, with a fungus growing on it. If the growth is cotton like (fungus). If the growth is tight on the fish, possibly Columnaris.