Gambusia affinis is a nice little  fish originally coming from Texas, now they are probably found on almost  every continent. They are called mosquitofish  and being a small and  temperate climate fish, they are good at removing mosquito larvae from puddles and other bodies of water and are also consider a pest in some parts because of being veracious eaters of other specie's fry . 

Also these fish are  carnivores and they will eat the fry unless you have  a heavily planted tank  with floating plants like Indian fern and you are vigilant in removing a large female as soon as she bears her young, you should have some success remember these fish are quick and very hungry for live food. The mosquitofish I had  where purchased at a wholesalers in  Glasgow just keep your eyes open and you should be able to find them

My general description of the average mosquitofish is fairly similar to that of the plain guppy the female mosquitofish are considerably bigger than female guppies when full grown to 3 in  Males might be 1-1/2 inches in length

keep them in a 2ft tank at 20-24c ph7-7.2 and you should have no difficulty in keeping them alive and with good feeding they should breed for you