Livebearers are generally fine by themselves. If you make sure that you get all males, you don't have to worry about the baby problem

Just don't get more than one male swordtail because they can get very aggressive toward eachother. Male guppies make a beautiful tank. I looked at your aquarium info and saw that you have a pleco. Is it a common pleco? If it is, it will grow up to 2 ft long, and it is cruel to keep him in a 10g tank. He will probably get sick and die at a very young age from stunted growth. Many LFS's sell them and tell the buyer that they will only grow to be the size of the tank, but that is not true. Bristle Nose Plecos or Clown Plecos would be good in a 10 gallon though
