Endler's livebearer

Quick facts

Adult size

3 cm

Lifespan

can live up to 3 years; captive average 1.5-2 years

Tank zone

top

Temperament

peaceful

Difficulty

beginner

Water parameters

Temperature

22–28°C

pH

7.0 to 8.0

Hardness

10 to 25 dGH

Tank requirements

Minimum volume

40 L

Minimum length

45 cm

Flow

low

Lighting

moderate

Substrate

any

Hiding spots

needed

Feeding

Diet: omnivore, feeds primarily at the surface.

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.

Habitat

Native to coastal lagoons in northeastern Venezuela, specifically Laguna de Patos near Cumana and a few nearby bodies of water. The species was observed by Franklyn F. Bond in 1937, then not seen again until John Endler rediscovered it in 1975, leading to some confusion about whether it had gone extinct. The original habitat is warm, shallow lagoons with dense algae growth and variable salinity. Wild populations are critically small and the habitat is degraded by pollution and introduced species. Essentially all fish in the hobby descend from captive-bred lines maintained by enthusiast breeders since Endler's collections in the 1970s. The males display some of the most vivid coloration of any livebearer: patches of metallic green, orange, black, and iridescent blue arranged in patterns that vary between genetic lines. Females are plain olive-gray. The classification situation is tangled: the species is sometimes listed as Poecilia wingei (described by Poeser, Kempkes, and Isbrucker in 2005) but whether it's genuinely distinct from P. reticulata (the common guppy) is still debated. In the hobby, fish are classified as N-class (verified pure wild-type lineage), P-class (phenotypically Endler's but unverified lineage), and K-class (known hybrids with guppies). N-class fish carry a premium and are tracked by specialist breeders.

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

Bioload coefficient: 0.5 (small body, similar to ember tetra; floor-lifted slightly above formula due to constant feeding pattern of livebearers).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

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