I am a newb so bare with me if this is a silly question, but do swordtails breed with other types of swordstails? Because I do not have a male and female of the same kind yet today I noticed that the black ones belly is rounder and larger than normal... I have isolated it for the moment in a breeder in order to try to get a good picture but in the picture I can barely tell what I am seeing with my eyes... I do not want to keep her in the breeder for fear that it will stress her but if you guys recommend that I should I will.