Guppies are among the most popular livebearers thanks to a combination of small size, bright colours, peaceful behaviour, adaptability, and hardiness. They are often recommended as ideal beginner’s fish, and to some extent that is justified, as few tropical freshwater fish are as easy to maintain or breed as guppies. But their tolerance for poor water conditions and slack aquarium management can be easily overestimated, and fancy guppies in particular are not nearly as hardy robust as their wild ancestors. On the other hand, in a properly maintained aquarium with suitable water conditions guppies are largely problem-free animals, and the ease with which they can be bred has made them attractive to generations of aquarists as well as educators and scientists.