sexing question

[zoowks]

so i kno angelfish are hard to sex, but if they are so hard to sex, how do angelfish know what sex the other angelfish is? and y can't we do it too?

a lil strange of a question but it struck me and bothered me since i figured it out

[Lupin]

There has been a few incidents actually of two females spawning together thus ending up in a whole batch of infertile eggs.;)