(Click the image to view larger version on Flickr)
The photo was taken from Canada's Wonderland. They seem happy and satisfied.
Koi carps are specifically known for their various colours, although the word "koi" just purely means "carp" in Japanese.
The shiny colours make them easy preys in any natural habitat. But people do believe these colours bring in fortune and happiness, so the breed survives and thrives, in garden fishponds of course.
Good thing? Bad thing?
The breed can't survive in natural environment, so no impact to the big ecosystem out there.
But their existence pleases our lives, just like garden flowers and pets, so why not.