Blood Red Swordtail Fertility Problems

[swordtail_king83]

anyone out there notice the blood red swordtail females (the ones that are a deep dark red with the black eyes) have a terrible fertility problem?? every single blood red female I have ever owned thru the years has never gotten pregnant. they remain slim throughout their entire lives. for the record I have a mass of floating plants on the top, always do, densely planted tank, separate females into their own "delivery" tank prior to birth when their "squared off". I have never seen a male sword of any color even try to mate a normal blood red female. like I said mine remain slim their whole life. and no there not a "late" male. I have them from buying them till they die of old age (3-5 yrs) same fan shaped anal fin, no sword, no thickening of anal fin. fed brine shrimp and earthwork flakes 3 x a day. so im thinking there is a fertility issue on the blood red lines. now the BRICK red sword females are always preg, #32### they get preg by looking at them I swear lol. here is a link to determining fertility in female xiphophorus based on body shape which explains my theory on why my blood red females are always slim..(no eggs produced inside them) yet other females even when not pregnant look pregnant (full of fertile eggs) just read this article. http/www.xhifin.org/ click breeding at the side of the page scroll down to "identifying fertile females". you will see 2 female swords of the same variety side by side in the same tank. one is slim and one is fat, neither is pregnant as they are virgin, but the fat one is full of eggs. so im thinking my problem is im not picking fertile blood reds. so what im thinking of doing is buying a MALE blood red, using him to breed any female and then using those blood red fry if females at maturity to breed with. anyone have any similar experiences in blood red females having fertility issues (not getting pregnant)