A school of koi fish swim in a dark tank. Bubbles rise to the surface of the water from an unseen source. A white koi fish with large fins swims in the foreground, its scales shimmering. Behind it, an orange and white koi fish swims, followed by a red and white koi fish. The fish are close together, suggesting they are feeding or schooling. The water is slightly murky, and the bottom of the tank is covered in dark gravel.