To follow on from my previous post, sexing goldfish is a little more difficult. There isn’t the colour differences and it will be difficult to distinguish between males and females in those bred for their rotund body shapes.
However, during the breeding season/spring time, male fish will develop little white nodules ~0.5mm in diameter on their operculae (gill covers) and along the anterior rays of their pectoral fins. And of course, you will notice males chasing the females when they are ready to spawn.
