aquarium fish: Guppy

The guppy prefers a hard water aquarium and can withstand levels of salinity up to 150% that of normal sea water, 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. Its most famous characteristic is its propensity for breeding, and it can breed in both fresh water and marine aquariums.

Guppy breeding by aquarists produces variations in appearance ranging from color consistency to fantails and "spike" swordtails. Selective breeding has created an avid "fancy guppy" collector group, while the "wild" guppy maintains its popularity as one of the hardiest aquarium fish.

Well fed adults often do not eat their own young, although sometimes safe zones are required for the fry. Specially designed livebearer birthing tanks, which can be suspended inside the aquarium, are available from aquatic retailers. These serve the dual purpose of shielding the pregnant female from further attention from the males, which is important because the males will sometimes attack the females while they are giving birth. It also provides a separate area for the newborn young as protection from being eaten by their mother. However, if a female is put in the breeder box too early it may cause her to have a miscarriage. Well planted tanks that offer a lot of barriers to adult guppies will shelter the young quite well. Java moss, Duckweed (Lemna Minor), and Water Wisteria are all excellent choices.