Ever have any fertilized eggs that turn into wigglers? If not, you may have two females or a sterile male or sterile female. A blue and a PB is not the best match and will probably produce poorly colored offspring, but if you can get some fry they will definitely be worth keeping and practicing on for future pairs. I have a nice blue carnation SS and a rose red that I'm doing the sme thing with shortly when I get them their own tank. I know they are fertile but the fry the produce will probably be ugly. I'd still like the experience of raising fry so I'm still going to work with them knowing the fry won't be worth much as it will be difficult to sell them.