Livebearers Just Wont Breed?

[phantomlink]

I know with guppies if the female doesn't consent the males will just force their way in and breed, but what about things like Platty and Swordtail? In my large tank I have 9 of them, 2 being male and 7 females ( I had more, but some have died off over the past month ) and I've had them for almost two months now and I've yet to have fry or a pregant female. Are the males just not doing a good enough job or do I have picky females? My only female guppy is pregnant I'm pretty sure right now so I will be trying to save all the fry I can

My next tank is going to be a 50-100 gallon active/shoaling tank and I want to include some live bearers in it. I will be adding some more guppies and might think about Swordtails. I might move the platy I have into it or get some more. I'll ask the local LFS if they will accept any fry, but if not I can always put the excess in my catfish tank I know some might seem it as cruel but I'd rather give my current fish some food then see fry starve or get sucked into filters/flushed and since feeder fish are deemed bad due to illness home bred fish should be better right?

 

[coyemuse]

I think it all depends on the fish. I have 3 female swords that are breeding age. And one male. Two of the females consistently get pregnant, but one self-aborts, and the other is my only dropper. The third one, has never been pregnant, and I've had her about 10 months now.

Also, I have 4 platys, same ratio, and only one has been pregnant in the 9 months I've had them