This is attributed to the selective breeding process of fancy goldfish to achieve particular body forms, such as that of the Pearlscale's roundness, which results in the alteration of the appearance of the shape and function of the swimbladder.

The Pearlscale standard is as follows: The fish should be bright and alert and displaying well developed domed scales all over the body area.

Calico fish should have a blue background with patches of violet, red, orange, yellow and brown, spotted with black.

[1] The breeding and marketing of fancy goldfish with extreme mutations is sometimes seen as cruel practice by fish keepers and animal rights activists.

Because the Pearlscale Goldfish has been bred to such a spherical shape, it may experience problems with its spine and internal organs, reducing its quality of life and longevity.