Guppies are one of the most common aquarium fish. Liked by beginners because they are easy to keep and breed and adored by enthusiasts who are into breeding fancy versions of guppies.
Many aquarium hobbyists start their career in the hobby by keeping guppies.
They are also wonderful for the young aquarist to learn the basics of Mendelian inheritance, simply because of the large number and combination of various traits that breeders like to establish in their prized strains.
Because guppies are easy to breed even an inexperienced aquarist can do it and see how various combinations of color, fin shape, and similar properties get passed from generation to generation. Establishing traits that breed true requires a lot more than that though.
On the topic of breeding guppies, check out following resources on the web: