Rainbow Goodeid

Rainbow Characodon
Characodon lateralis

Günther, 1866

Also known as: Rainbow Goodeid, Red Prince, Mexclapique arcoiris

Max Size: 4 cm TL (males) / up to 5.5–6.5 cm SL (females)

One of the most vividly colored goodeids in the hobby. Both sexes start olive-brown, but adult males become the showpiece: reddish to deep-red flanks, bluish-green scale iridescence, and unpaired fins banded in red, orange, or yellow with a broad black terminal edge. That fin pattern is the “rainbow” that gives the fish its name. Females stay more muted — olive-brown with a creamy or yellowish belly, clearer fins, and two to seven dark midline blotches. Males also carry the classic goodeid splitfin (notched anal fin / andropodium). Color intensity varies by population and age; older males are usually the reddest.

Characodon is the most basal living lineage of the typical goodeids (Goodeinae), having split from the rest of the family some 10–15 million years ago. Individual spring populations differ in color and body shape and should be kept as separate lines.

Origin & Habitat
Endemic to highland springs and spring-fed ponds in Durango, Mexico, in the upper Río Mezquital basin (around 1,800 m elevation). Classic localities include Los Berros (Ojo de Agua Los Berros), a tiny private spring at La Constancia, and historically San Juan, Nombre de Díos, and Amado Nervo. It prefers shallow water (usually under 0.5 m) with little or no current, clear to turbid, over silt, mud, sand, gravel, or rock, with dense submerged plants such as Myriophyllum, Ceratophyllum, Potamogeton, Scirpus, and water lilies. Typical parameters: 18–24 °C (up to ~27 °C in nature), pH 6.0–8.0, hardness around 9–19 dH.

Diet
Omnivore with a carnivorous lean. Adults take small invertebrates, aufwuchs, diatoms, and filamentous algae. In the aquarium offer high-quality flakes or granules plus live or frozen foods (daphnia, brine shrimp, bloodworms) and some green matter (algae, spirulina, blanched spinach or peas).

Behavior & Temperament
Generally peaceful for a goodeid, though males can be territorial toward one another. Best in a planted tank with open swimming space and plenty of cover so rival males can space out and fry can hide. Occupies the lower to mid levels and is not especially shy once settled.

Reproduction
Viviparous livebearer. Embryos are nourished through simple ribbon-like trophotaeniae. Gestation lasts about 50–55 days; females produce 5–20 relatively large young. Sexual maturity is reached in roughly five months. In the wild, breeding runs mainly from March through September.

Conservation Status
IUCN: Critically Endangered (CR).
Mexican NOM-059: En Peligro de Extinción.

The wild range has collapsed to a handful of springs. The Amado Nervo population is extinct in the wild; remaining fish persist mainly at Los Berros and a very small spring at La Constancia, often in low numbers and sharing the water with invasive swordtails, tilapia, bass, gambusia, and crayfish. Groundwater pumping, pollution, and habitat alteration continue to shrink what is left. Captive breeding in Mexico, the United States, and Europe is now essential, and locality strains should never be mixed.

A highland-spring jewel whose males flash red, gold, and black — and a species that now depends as much on aquarists as on the last Durango springs that still hold it.