Sky fish

Sky fish were native to Kazran Sardick's planet. They were able to swim via electricity in the crystalline fog of the planet. The fish were attracted to music, as it resonated the crystals in the fog and caused pleasing delta waves.

There were many species of sky fish, ranging from finger-sized, guppy-like creatures to giant sky sharks. They where common prey to Sky Sharks as The Doctor witnessed when a Sky shark ate a Sky Fish and half of his Sonic Screwdriver. (DW: A Christmas Carol)