Livebearers prefer larger tanks with a lot of floating plants in them. Plants like Hornwort, Anacharis and Pennywort are good ones. If you have a bit higher lighting, then float Water Sprite in the tank. These plants are natural water filters and make good hiding places for the females and eventually, the fry.
Don't move any fish. It's stressful and unnecessary. Just feed all the fish a little more and a little more often. If you like, put some flaked fish food into a heavy sandwich bag and using a rolling pin to mash it up.
I feed mostly frozen foods from San Fran Bay, freeze dried tubifex worms from Hikari or Tetra and flakes from Cobalt.
Don't neglect your water changes. Tanks up to 30 gallons should have half the water replaced weekly. Larger tanks can typically go 2 weeks between 50 percent changes. The water in very small tanks should be changed every 2 to 3 days.
This isn't the only way to do things. The water keeping hobby isn't an exact science. There are many ways to succeed.
"Fear not, my young apprentice. Just change the tank water."