The guppy (Poecilia reticulata), also known as millionfish and rainbow fish, is one of the world’s most widely distributed tropical fish, and one of the most popular freshwater aquarium fish species.

Guppies prefer a hard-water aquarium with a temperature between 25.5 and 27.8 °C (78 and 82 °F) and salt levels equivalent to one tablespoon per 19 l. They can withstand levels of salinity up to 150% that of normal seawater