Black markings

[Chaory 21]

Just want to know what these black markings are.

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[Arctic Mama 3,641]

I can't see clearly in the photo because of the light and focus.  Usually though, black markings that look like smudges or dustings of black are melanophore migration, which comes when a wound is healing.  Ammonia burns or other chemical burns, mechanical damage like getting stuck on tank decor or spawning injuries, and even healing sites from where parasites have been attached can all generate melanophore migration when the goldfish begins healing.

 

It fades on its own within 3-6 weeks.

[Chaory 21]

I can't see clearly in the photo because of the light and focus.  Usually though, black markings that look like smudges or dustings of black are melanophore migration, which comes when a wound is healing.  Ammonia burns or other chemical burns, mechanical damage like getting stuck on tank decor or spawning injuries, and even healing sites from where parasites have been attached can all generate melanophore migration when the goldfish begins healing.
 
It fades on its own within 3-6 weeks.

Thanks, I remembered a few weeks ago, she got stuck in the Aqueon water changer. Though the water was filling up the tank, she somehow managed to swim into it. I saw what was happening and lift the tube and she got out. This is why I use a pump to drain the water, but somehow this one was naughty enough to go into it.

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[Arctic Mama 3,641]

Yes, I'd definitely suspect that was the cause in the absence of other symptoms.