Ah ok, didn't know about that lovely_goldfish. I would have asked "How would you know if your gf is male or female", to be completely safe
Anyway I can't usually tell by the claudal fin thickness whether they are male or female. At the moment I am using the innie-outie rule...but if I were to do that, all my goldies will be female! (bad eyesight on my part

) But I noticed one of them is not thattt much of an outie, so I reckon it's male. Oh...and you cannot tell the male/female difference when they have poo right?
There, I demonstrated not using sex/gender in my question woo hoo