Endler's livebearer

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

Takes any small food: crushed flake, micro pellets, frozen baby brine shrimp, frozen daphnia, frozen cyclops, live microworms, and vinegar eels. The mouth is small, so standard-sized flake needs to be crushed. They feed primarily at the surface and in the upper water column. Algae and biofilm grazing supplements the diet in established tanks. In shrimp tanks, they'll eat shrimp food without conflict. Feed twice daily in small amounts. Overfeeding is the main risk because the fish are tiny and produce waste proportional to intake, which fouls nano tanks quickly.

Compatibility

• Same genus as the common guppy (Poecilia) and interbreeds freely with them. Housing Endler's with guppies produces hybrid offspring that lose the distinctive wild-type patterning within a generation or two. If maintaining pure N-class Endler's matters to you, keep them in a species-only tank.
• Peaceful and tiny. Males top out around 2.5 cm, females around 3.5 cm. Any fish large enough to fit them in its mouth will eat them. Stick with nano tankmates: small tetras, rasboras, shrimp, snails, and other livebearers of similar size.
• Males display constantly, chasing females and flashing color at rival males. This behavior is harmless but relentless. Females need a ratio of at least 2-3 females per male to distribute the attention. A tank of all males is also fine and avoids the exponential population growth.
• Shrimp-safe. Adults and fry coexist well with cherry shrimp and other Neocaridina. The mouths are too small to eat anything but the tiniest shrimplets.

Origin and habitat

Native to coastal lagoons in northeastern Venezuela, primarily Laguna de Patos near Cumana and the Campoma region. First collected by Franklyn F. Bond in 1937, then rediscovered by Dr. John Endler in 1975. Endler's collections were the first to reach the aquarium trade; more have been collected since, notably by Armando Pou. Laguna de Patos was originally a brackish lake cut off from the ocean by a sandbar, now freshwater due to runoff. The original population is threatened by a municipal garbage dump and was believed extinct for a period. IUCN listed as endangered as of 2024. Formally described as Poecilia wingei by Poeser, Kempkes, and Isbrücker in 2005, named after Danish biologist Øjvind Winge for his work on guppy color genetics. Schories et al. (2009) confirmed P. wingei as a valid species distinct from P. reticulata via molecular phylogeny, though the two hybridize freely producing fertile offspring. Endler himself has said most hobby fish are now hybrids. The hobby uses a classification system: N-class (traceable to native Venezuelan waters), P-class (phenotypically Endler but unverified origin), K-class (known hybrids with guppies). Males display vivid metallic green, orange, black, and iridescent blue patches; females are plain olive-gray.

Breeding

Livebearer that breeds faster than common guppies. Females produce 5-25 fry every 23-28 days with no seasonal trigger required. Fry are relatively large at birth (about 5 mm), fully formed, and immediately free-swimming. They can eat crushed flake and baby brine shrimp from day one. Females can store sperm for multiple broods from a single mating, so even a lone female purchased from a mixed tank may produce fry for months. In a species tank without predators, population growth is exponential and can overwhelm a small tank within a few months. Controlling the population requires separating sexes, adding a predator (a single female betta works), or regularly rehoming juveniles. Pure N-class breeding stock should not be crossed with guppies or unverified Endler's if maintaining lineage purity is the goal. Males are sexually mature at about 3-4 weeks; females at 6-8 weeks.

Common problems

Hybridization is the main concern for keepers who care about lineage purity. Most fish sold as 'Endler's livebearers' in general pet stores are hybrids with guppies (K-class). True N-class fish are available from specialist breeders and livebearer clubs but not from chain stores. If purity doesn't matter, the care is identical regardless of class. Overpopulation from unchecked breeding crashes water quality in small tanks. A colony that starts with 6 fish can reach 50 within a few months. Regular culling, separation of sexes, or predator addition keeps numbers manageable. Health-wise, Endler's are tough. They tolerate a wide range of water conditions (pH 6.5-8.0, GH 5-25, temperature 22–28°C). Diseases are uncommon in established tanks. Fin rot occasionally appears in males with elaborate finnage, usually from a minor injury that gets infected. Mycobacterial infections (wasting disease) crop up in some inbred lines.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size