There are many strains of swordtail fish. I like the pineapple strain, there are others I like too, but are harder to find at fish stores. These fish are the biggest of the the livebearer group(there are some big mollies too).
I was never able to breed them at home. I had to buy one pregnant female at the store, and in the way home she had half of her fry, but the fishtanks were almost full. Only five of fifty survived. Then when I decided they were a little bit big(10 weeks old), I dared to put them with some diamond tetras and keyhole cichlids. It was a deadly mistake. They ate them alive.
Swordtails take their time to grow. Maybe one day I will buy another pregnant female and dedicate more time raising their fry(at least once).