Guppies are fun fish for families as they grow quickly and provide several years of fish watching and broods of fry. Good water conditions with filtration and an environment that looks natural is about all you need to ensure guppies will breed. They are an easy keeper and multiply rapidly. Provide excess room in aquariums for the broods to move into, so everyone has enough space in their environment.
Guppies are ovoviviparous, meaning they mate internally, as opposed to some fish who lay eggs and then the male fertilizes them. The male guppy's anal fin develops into a gonopodium, their sexual organ, to transfer sperm into the female's cloaca. The gonopodium has hooks on the end to secure the male into the female for breeding.
The Female Wonder
Female guppies are unique in the fact that she retains sperm in her genital region in special folds to allow her to produce several broods without male insemination for each.