Tetra with black area on back

[laurarenee]

I have had a tetra for over a year now...about 6 months ago he started to develop this spot that has since grown...he eats fine, acts fine. I've been treating my tank with "Lifeguard All in One" ...on day 4 now with no signs of improvement. Any thoughts on what it is and what to do? All other fish are perfectly healthy.

 

[Coursair]

He looks like a dyed or gene modified Skirt Tetra. As that is not a natural color, I don't know the long term consequences.


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