Last summer I was putting together a biotope aquarium, using all native species of fish and plants collected from local water sources (with permission). Never got finished so all fish were released with the exception of one baby carp that was about 2 inches long at the time. Its colour up until about a month ago was a dark gray (almost black) along the spine (blended very well with dark bottom), and a beautiful metalic silver along its sides. In other words, a very fishy looking fish.
About a month ago it started loosing colour. At first I thought it was a disease, but it started getting yellow. This continued up until the present day where it is now a VERY bright yellow-orange with black patches. Almost as if it were a goldfish.
Now I understand that some people have released goldfish into the wild, but Im very sure this isnt a wild variety. For one, it was too silver, and for another, it was too big to be a juvenile goldfish when captured.
Can anyone suggest how/why this thing changed colour? Is it even a carp? (the shape is consistent).
It has been kept this whole time with 2 mature goldfish, and is fed flake food.