Why does everyone say its impossible to sex an oscar?

I know how to sex oscars, but some oscars are more difficult than others.Why does everyone say its impossible to sex an oscar?What's your magic skill then? Oscars are monomorphic, no external differences between the sexes. And behaviour is not a clue, a male and female would chase each other, as would a male/male or even female/female.



A mature female that's paired with a male however may begin to look more full in the belly and you'll see their breeding tubes when they spawn, but that's the only time they have any external differences between the two sexes.



edit: You mean venting, some people swear by that others say it doesn't work.



The one on the left is male the one on the right is female:

http://www.flippersandfins.net/Images/Os鈥?/a>

Pretty darn subtle and still doesn't work 100% of the time.



This is the only time you can really tell, when you see their breeding tubes. Males being thin like a thorn and a females being broad and thick.Why does everyone say its impossible to sex an oscar?sex oscars = porn academy awards?