gender differentiation in goldfish

[emi-chan]

i'm sorry but how do you tell if a goldfish is male or female?
i've heard that males have those white dots thingys on their gills so does that mean they're female if they dont?
my two never stay still enough for me to have a good long look at them!

[Diana]

Mature males in breeding condition will develop breeding tubercles on the head, gill plates and even the front fins. Location and quantity varies a bit.
I am not sure how old or what size the fish need to be to develop them, but I really doubt that Golds under 3" would show any, and maybe they have to be even bigger.

They are not on the fish all the time, and not on young fish.

[emi-chan]

well i've had these goldfish a good bit longer than my brother has had his and mine are bigger too. his fish have shown the tubericle things (except the smallest one) and mine have never shown them. is it a safe to guess that they're female then?

[Diana]

Probably.