The guppy (Poecilia reticulata), also known as the millionfish, is one of the most popular freshwater aquarium fish species in the world.

It is a small member of the Poeciliidae family [females 4–6 centimetres (1.6–2.4 in) long, males 2.5–3.5 centimetres (1.0–1.4 in) long] and like all other members of the family is live-bearing.

The guppy prefers 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 5 US gallons (19 l; 4.2 imp gal).  They can withstand levels of salinity up to 150% that of normal seawater, which has led to them being occasionally included in marine tropical community tanks, as well as in freshwater tropical tanks. Guppies are generally peaceful, though nipping behaviour is sometimes exhibited between male guppies or towards other top swimmers like platys and swordtails, and occasionally other fish with prominent fins, such as angelfish. Guppys shouldn't be kept as a single fish in an aquarium because both males and females show signs of shoaling, and are usually found in large groups in the wild. Its most famous characteristic is its propensity for breeding, and it can breed in both fresh water and marine aquariums.

Click on any of the images below to view our Guppy gallery.