I purchased 2 marbled hybrid Yucatan mollies at Pet Smart about six months ago. Initially I needed two inexpensive fish to cycle a tank. I chose a pregnant female and a stunning male. I put them in a 10 gallon tank that I was cycling. I added a Panda Cory about a week later. The female had her babies between the 3rd and 4th week of cycling the tank. I moved the male to the 55 gallon tank and left the female and her babies in the 10 gallon.
As you may know a live bearing fish can give birth several times without needing a mate each time. I let the female stay in the 10 gallon until I had a total of 6 – 7 of her surviving babies, before moving her up to the 55 gallon to breed again.
Though I have had mollies in the past, I generally chose the little solid black mollies (poecilia sphenops) who rarely eat their babies. Yucatan mollies, are a bit more aggressive and will readily eat their babies if the tank is not well planted with plastic or natural plants.
The difference between a Sailfin molly (P. latipinna,) and a Yucatan molly is the number of rays in the dorsal fin. The sailfin has 15 rays and the yucatan has 20 rays.