What is the best fish birth method?

So I'm pretty certain my Swordtail is pregnant. I'm very happy! But I have seen two methods of birth. I only have a 20 gallon tank. So it's not like I have room for every fry. But I would like to keep as many as possible. I'm not sure how many in a "litter" (don't know what to call it with fish) I know some people put the pregnant fish in a net isolated from others to give birth. However I've heard that sometimes the female gets very stressed and can die. Also I've heard that you can let nature work it's self out. Survival of the fittest. That seems kinda cruel I don't want any to get eaten. But I don't want to risk losing one of my beloved swordtails. I do have a very small tank about 1.5 gallons I think. Maybe I could put the fry in there after noticing any survivors? All help is appreciated! Thanks!!