How Can You Differentiate Male Or Female Fishes? Options

[steffie]

How can you tell if the goldfish is male or female when they're still young?

I know that you could tell by the tubercles when they're older, but how about when they're young ?

And how do you know how old is the goldfish, by telling it from their size without taking off a scale and count the rings on the scale with a good mircoscope?

How big is 1 yr old goldfish? how about 2 yrs / 3 yrs old?