If you want to breed guppies (or any livebearer), your best bet is to have a tank of females only and have males in a different tank. When livebearers mate, the males deposit several sperm packets in the female. The female then uses these individual sperm packets to fertilise a batch of eggs. The eggs develop inside the female before she gives birth to live young. If conditions are good (and they usually are in an aquarium), the female will develop another batch of eggs within a week or so of giving birth. This next batch of eggs will be fertilised by one of the remaining sperm packets she is carrying in her body.
This process of giving birth and fertilising new batches of eggs continues until the female has used up all the sperm packets that she is carrying. They can carry 6 or more sperm packets at any time.
If you keep the females separated from males until they have used up all the sperm packets, then the females can have a month or two rest and then you can breed them again.
With swordtails, keeping males and females separate does not always work. If female swordtails are kept without a male and are unable to breed, they can change sex. The biggest most dominant female can turn into a male and breed with the remaining females. however, it is still a good idea to separate male and female swordtails for a while so the females aren't being continually harassed by the males.
This process of giving birth and fertilising new batches of eggs continues until the female has used up all the sperm packets that she is carrying. They can carry 6 or more sperm packets at any time.
If you keep the females separated from males until they have used up all the sperm packets, then the females can have a month or two rest and then you can breed them again.
With swordtails, keeping males and females separate does not always work. If female swordtails are kept without a male and are unable to breed, they can change sex. The biggest most dominant female can turn into a male and breed with the remaining females. however, it is still a good idea to separate male and female swordtails for a while so the females aren't being continually harassed by the males.