How do you know if a one-tailed goldfish is male?

Answer by  sanityrose (2664)

The best time to find out your one-tailed gold fishes sex is during their mating season. Any other time is a shot in the dark, the bigger fish is often the female. When in the breeding cycle a male will have 'breeding tubecles' on their head and gills. The tubercles are white and often describes as 'prickely'.

Answer by  Liz59 (10966)

It depends on where the gill is located. If the gill is located directly under neath the throat of the goldfish, then it is a male goldfish. A female goldfish also has a curvier body. It is more circular in nature and that is how you can tell the difference.