Yes I have only one of each fish, I do know that they are kept better with school of their own species but I have noticed my cherry barb and rainbow fish had developed a bond with each other. They are always next to each other so I did not bother putting any more fish in because they looked happy. Thanks to every one for the infoI don't think mollies and rainbowfish are compatible. Mollies like their water harder and warmer.
Don't go brackish with those fish.
Have you got just one of each fish?