Hello

Ok, so I read that they are egg layers... what do the eggs look like? How do you even tell if they are pregnant? Ours has a belly, but I didn't know if there were certain spots ot something like with the swordtail. Are females genreally wider, not as thin? I am having a hard time sexing my black skirts. I just think one is pregnant. Also, are black skirts the same fish as the blav tetras. I read some posts refering to black ones, but didn't know if they were the same. Thanks for your help
Angie