Taxonomy & naming
Neoheterandria elegans was described by Arthur Wilbur Henn in 1916 and placed in the genus Neoheterandria within the family Poeciliidae — the New World livebearers that also contain the guppies, mollies, platies and mosquitofishes. Eschmeyer's Catalog of Fishes is the authority for the valid name; FishBase places the species in the order Cyprinodontiformes, family Poeciliidae, subfamily Poeciliinae, under SpecCode 46771.
The genus name Neoheterandria is built from Greek roots — neos, "new," combined with heteros, "other," and andros (anēr), "male" — a construction that echoes the related genus Heterandria and points, as so many poeciliid names do, to the distinctive modified male anal fin. The specific epithet elegans is Latin for "elegant," a fitting description of a neatly barred, jewel-small fish.
The genus Neoheterandria is small and centred on the lowlands of Central America and northwestern South America. N. elegans is the diminutive member of the group and the one most familiar to aquarists, where it circulates under the FishBase common name "Orange dwarf toothcarp" and the widely used hobby name "Tiger Teddy."
Morphology
This is a genuinely tiny fish. FishBase gives a maximum length of about 1 in total length for males and unsexed individuals, with females reaching roughly 1 in; hobby measurements agree closely, putting mature males near 0.5 in and females around 1 in, with sexual maturity reached at only about half that length. Few aquarium fishes are smaller as adults.
The body is tan to olive at base colour and marked with a series of bold dark vertical bars — typically eight or nine — running down the flank, the pattern that earned the fish its "Tiger Teddy" nickname. A gold spot often shows mid-flank, and the overall effect on a well-conditioned fish is of a striped miniature far more striking than its size suggests.
Sexual dimorphism is clear once the fish are grown. Males are markedly smaller and slimmer than females and carry the gonopodium, the rod-like intromittent organ formed from modified anal-fin rays that is the structural signature of the live-bearing poeciliids. Females are larger, deeper-bodied and plainer, and in breeding condition the dark abdomen of a developing brood may be visible.
Habitat
Neoheterandria elegans is a narrow endemic. Its range is given as the Río Truandó, a tributary of the Río Atrato in Colombia, and the fish is believed to be restricted to that drainage — a small footprint that puts it among the more geographically limited poeciliids kept in the hobby. The Atrato system drains the wet Pacific-Caribbean lowlands of northwestern Colombia, one of the rainiest regions on earth.
The species is a freshwater, pelagic fish of tropical waters. FishBase records a preferred temperature range of roughly 75–82 °F (from Wischnath's Atlas of Livebearers), consistent with its warm lowland origin. Hobby accounts report success in neutral, slightly soft water, though some keepers note tolerance of harder water as well.
Whatever the exact chemistry, water quality matters more than precise numbers for this fish. Aquarists consistently describe N. elegans as intolerant of poor conditions — a small, delicate species that fares badly in neglected or unstable water, which is the single most important fact to carry over from its habitat into its care.
Feeding
Neoheterandria elegans is a micro-predator. FishBase places it at a trophic level of about 3.0, the level of a small-prey predator rather than an algae-grazer, and both wild ecology and aquarium experience point the same way: this is a fish built to hunt tiny moving food.
In the aquarium it takes finely crushed quality flake, but keepers regard small live and frozen foods as essential rather than optional. Newly hatched brine shrimp, microworms and similarly sized items keep the fish in condition and bring out the best colour and breeding response. Because the mouth is minute, everything offered must be correspondingly small.
The constraint is most acute with fry, which are extremely tiny even by livebearer standards and may refuse flake during their first week of life — newly hatched brine shrimp and other live micro-foods are needed to get them feeding and growing. For both adults and young, frequent small feedings of appropriately sized food suit the species better than large meals.
Mating
Like all poeciliids, Neoheterandria elegans practises internal fertilisation. The male transfers sperm to the female using the gonopodium — the slender intromittent organ formed from modified rays of the anal fin — rather than fertilising eggs externally. Reproduction follows the familiar livebearer pattern in which the male pursues and chases the female and effects sperm transfer when he can draw alongside her.
The pronounced size difference between the sexes — small, slim males and notably larger females — is typical of the dwarf poeciliids and shapes this courtship: a male a fraction of the female's bulk darting in to make contact. As in other members of the family, females can retain viable sperm internally, so a single mating can fuel a succession of developing young over time.
The hobby literature describes the mating system as straightforwardly poeciliid in mechanism, with no elaborate display or nest-building; the distinctive feature of this species lies not in how it mates but in how the resulting young are spaced out, through superfetation, as described below.
Breeding
Neoheterandria elegans is a viviparous livebearer that bears free-swimming young rather than laying eggs — but it does so in an unusual way. The species is superfetatious: a female carries broods at several stages of development simultaneously and releases young a few at a time rather than dropping a single large brood. FishBase records that "one to two young are born at intervals of 2 to 4 days," and hobby accounts describe a small number of fry trickling out across the breeding cycle, often with a few (roughly two to five) appearing after a weekly water change.
This low, continuous output is the defining reproductive trait of the fish and a sharp contrast with prolific livebearers such as the guppy, which drop dozens of fry at once. Superfetation spreads the reproductive investment across time, so an established pair or small group produces a steady trickle of young rather than periodic large broods.
Raising the fry is the real challenge. They are exceptionally tiny — too small to take flake in the first week — and need live micro-foods such as newly hatched brine shrimp to start. Dense planting gives the delicate young cover, and because they are weak swimmers, only the gentlest filtration is appropriate. With patience, a healthy colony will slowly build itself up through this continuous, small-scale recruitment.
In the aquarium
Neoheterandria elegans is a nano-fish for a careful keeper rather than a beginner's livebearer. Its great virtue is its size: a heavily planted 5-to-10-gallon (roughly 20-to-40-litre) tank can house several pairs, making it ideal for small dedicated set-ups where larger livebearers would not fit. Keepers report success keeping three or four pairs in such a tank.
Water quality is the make-or-break factor. The species is intolerant of poor water, so regular partial water changes — keepers commonly do around 25% weekly — are part of routine care, and the fish does best in stable, clean conditions. Reports point to neutral, slightly soft water as a safe target, though some keepers find the fish tolerates harder water; consistency matters more than chasing an exact value. A gentle sponge filter is strongly preferred, because both adults and especially the tiny fry are weak swimmers easily knocked about by strong current.
A heavily planted aquarium serves several ends at once: it supplies the cover this small, shy fish wants, gives fry refuge, and helps maintain the clean, stable water the species needs. Tankmates should be chosen with the fish's minute size in mind — at under 1 in, N. elegans is best kept in a dedicated tank or only with the smallest, most peaceful companions.
Conservation
The IUCN Red List assesses Neoheterandria elegans as Data Deficient (DD), with the assessment dated 10 October 2014. A Data Deficient listing means there is not enough information on the species' distribution, population or threats to judge its conservation status — not that it is necessarily secure.
That caution is worth weighing against the species' apparent narrow endemism: it is believed restricted to the Río Truandó in the Atrato drainage of Colombia. A fish with so small a known range is inherently more exposed to localised habitat change than a widespread one, even where direct evidence of decline is lacking. FishBase notes high resilience and low vulnerability to fishing pressure for the species, but these are generic life-history estimates rather than population assessments.
For aquarists the practical takeaways are modest but real: the fish in the hobby derive from a limited natural source, captive lines are worth maintaining responsibly, and — as with any livebearer — surplus fish should never be released into local waters. CITES and CMS have not evaluated the species.