Common / Comet
A variant of Goldfish (Carassius auratus)
Representative Goldfishphoto — a dedicated image of this exact morph isn't available yet.
The hardy, streamlined single-tailed goldfish; the Comet is a slimmer American-bred line with a long flowing single tail.
Keeper tips for this variant
These are pond fish that hit 10-12 inches and are too large/fast for fancy tankmates — give them a pond or very large tank, not a bowl, and never house with delicate fancies that can't compete for food.