I don't think 1 gallon is sufficient for guppies. In my humble opinion, bettas are the exception to the tank size rules because of their labyrinth organ and the fact that they are so hardy, they can survive in small containers. From what I've gathered in the net, guppies need at least 5 gallons with a filter (cycled tank), they are social fish and should not be kept alone. Neither should you keep more males than females, or the males will stress them by chasing them too much. Ideal proportion is 1 male and 2 females, or what they call a trio. They are much easier to breed than bettas, you won't have to do a thing. Once pregnant, they'll give birth about every month. But they might eat the babies, so you'd need either a breeding trap/breeding net, or lots of plants for fry to hide in.
