Goldfish
The goldfish ("Carassius auratus") is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is one of the most commonly kept aquarium fish.
Pristella maxillaris
Older aquarium books often refer to this species by the junior synonym "Pristella riddlei". Aquarists tend to refer to this fish as the golden pristella tetra, though some call it the X-ray tetra, instead. Other common names include goldfinch tetra, a reference to the similarly coloured goldfinch, and pristella tetra, a modification of its Latin name. A common name that was once widespread but is now rarely used is signal tetra, a reference to the similarity between the yellow and black dorsal fin and the arm of a semaphore railway signal.