Butterfly Goodeid (Ameca splendens)

Ameca splendens, the Butterfly Splitfin or Butterfly Goodeid, is a striking and highly significant livebearer native to Mexico — specifically the Ameca River and spring system in Jalisco state. This species is considered Critically Endangered by the IUCN and is believed to be functionally extinct in the wild due to habitat loss, water extraction, and introduced species. The aquarium hobby represents a crucial refuge for this species.

Males are attractive: a grey-silver to olive body with a vivid black caudal fin edged with a brilliant yellow margin, giving the tail fin a 'butterfly' appearance. Blue-green iridescence is visible on the flanks under good lighting. Females are less colourful but larger, with a rounder body.

As a goodeid livebearer — distinct from the more common poeciliid livebearers (guppies, mollies, platies) — Ameca splendens gives birth to fewer but more fully developed young after an internal gestation connected by a primitive placenta-like structure. Fry are large and immediately capable of feeding on standard small foods.

Goodeid fish are frequently part of conservation breeding programs coordinated through the Goodeid Working Group (GWG), and aquarists keeping this species may contribute valuable individuals to these efforts. The Butterfly Goodeid is hardy, active, and interesting to keep — offering aquarists both beauty and conservation purpose.

Tank Setup: A minimum 80-litre aquarium for a group of four to six. Moderate to strong water flow, robust plants (they nibble soft plants), driftwood, and rocks. Good filtration. A lid is recommended — active swimmers can jump.

Water Parameters: Temperature 18–26°C; pH 7.0–8.0; GH 8–20 °dH; KH 5–12 °dH. Prefers slightly hard, neutral to slightly alkaline water — reflective of Mexican highland spring chemistry. Tolerates cool water unusually well.

Feeding: Omnivore with herbivore tendencies. Feed quality flake, pellets, blanched vegetables (zucchini, lettuce, spinach), frozen Daphnia, and brine shrimp. Feed two to three times daily.

Tank Mates: Can be kept with other robust, medium-sized community fish. Active and somewhat nippy toward each other but generally peaceful with other species. Avoid very small or slow fish.

Behaviour: Active and lively. Males display to females and compete with each other. Not as nippy toward other species as some goodeids. Females give birth to 5–25 relatively large fry after a 60–70 day gestation.

Health: Hardy and disease resistant. More cold tolerant than tropical fish. Weekly water changes of 25% maintain health. Avoid sustained temperatures above 28°C.