Rams gender

[Newbneedshelp]

I want to know if there is a good way of telling a German Blue Rams gender that i could use at a LFS. Im looking into breeding them and i dont want to have to buy 6+ to get a male and female. Also, if they are the only ones in the tank will they definitely pair off?

 

[TCTFish]

Very simple...girls have pink bellies