Butterfly Splitfin Goodeid: Caring for Ameca splendens
- aquaterraobsession
- Sep 11
- 10 min read
Comprehensive Biotope and Aquarium Care Sheet
:
This care sheet is designed for advanced aquarists, conservation breeders, and biotope enthusiasts. Its aim is to detail every aspect necessary to understand, care for, and breed Ameca splendens successfully, while supporting broader conservation outcomes.
Table of Contents
Habitat Community: Coexisting Species
Aquatic Plant Species Table
Introduction
The Butterfly Goodeid (Ameca splendens), also commonly called the Butterfly Splitfin, is a unique, vibrant livebearing fish endemic to central-western Mexico’s Ameca River basin. Beyond its striking appearance—with metallic scales, bold fin patterns, and fascinating social behaviors—Ameca splendens harbors immense scientific value as a model of evolutionary adaptation and reproductive strategy. This species is especially prized by aquarists who are drawn to natural or "biotope" aquariums that authentically replicate native Mexican aquatic habitats. However, the Butterfly Goodeid also stands at the crossroads of conservation: wild populations teeter on the edge of extinction due to habitat degradation and competition from invasive fishes.
Taxonomy and Species Overview
Scientific Classification and Etymology:
Taxonomic Rank | Classification |
|---|---|
Kingdom | Animalia |
Phylum | Chordata |
Class | Actinopterygii |
Order | Cyprinodontiformes |
Family | Goodeidae |
Genus | Ameca |
Species | Ameca splendens |
Etymologically, "Ameca" refers to both the genus and the river system where the fish was first collected, while "splendens" is derived from Latin for "shining" or "glowing," referencing the fish’s striking coloration. The species was officially described by Miller & Fitzsimons in 1971.
General Description: Ameca splendens is the sole species in its genus, notable for robust, laterally compressed bodies. Males feature vivid metallic blue to turquoise sides, a broad black vertical stripe on the caudal fin, and a terminal yellow or orange band. Females are larger, with greener bodies and duller, clearer fins often speckled with black dots. Adults typically range from 7–8 cm (males) to 10–12 cm (females), though some sources give maximum lengths up to 12 cm for exceptional individuals.
The most compelling behavioral features are their social dynamics: a “pecking order” forms in groups, especially among males, often manifesting as dominance displays, fin flaring, and coloration shifts. Notably, these fish are livebearers (viviparous) but differ from common poeciliids (guppies, mollies) due to their unique form of parental provisioning via a trophotaenia—a structure akin to a mammalian umbilical cord.
Native Distribution and Conservation Status
Historical Range: Ameca splendens was once widespread across multiple springs, streams, and pools in the Río Teuchitlán, a tributary of the larger Ameca River in Jalisco, Mexico. Its type locality is the spring pools near the town of Teuchitlán, though it also dispersed to nearby basins including Presa La Vega and the Sayula valley.
Present Day and Conservation: Wild populations have been decimated by pollution, habitat modification, and the introduction of exotic species such as tilapia and poeciliid livebearers. Currently, Ameca splendens is classified as Critically Endangered on the IUCN Red List, with most sources referring to it as extinct or nearly extinct in the wild, though a small remnant persists in the El Rincón waterpark and possibly reintroduced sites near Teuchitlán.
Legal Status and Projects: Mexico’s NOM-059-SEMARNAT lists the Butterfly Goodeid as in danger of extinction. International projects led by universities, zoos, and hobbyist consortia seek to reintroduce captive-bred strains into suitable wild habitats, typically in conjunction with river and spring restoration efforts.
Notable Introductions: Feral populations have been documented (though now likely extirpated) in Rogers Spring, Nevada, stemming from aquarium releases.
Natural Habitat and Ecology
Water Chemistry and Physical Parameters
Ameca splendens is a specialist of clear, warm, and hard alkaline waters, with key physicochemical properties:
Temperature: 20–28°C (occasionally up to 30°C in shallows)
pH: 7.0–8.0, but usually towards alkaline
Hardness (GH): 12–25 dGH; Total Dissolved Solids (TDS): 179–357 ppm
Water Type: Freshwater, consistently well-oxygenated (often above 8 mg/L O₂ in springs)
Flow: Moderate to brisk in springs and spring outflows, with some more stagnant backwaters after rainy periods
Depth: Most commonly found in shallow spring pools to 1.2m, but also in deeper, slow-flowing channels
Seasonal Variation: Springs maintain relatively constant temperatures, but associated streams show more diurnal and seasonal fluctuation.
Water parameters are determined by local geology—primarily limestone bedrock—yielding high mineral content and buffering against acidification. Clarity is typically high, though cattle and agricultural impacts can cause temporary turbidity.
Substrate and Hardscape in the Wild
Substrate
The natural substrate composition is varied, generally a mosaic of the following:
Fine sand and mud: Often comprising the main substrate in calm areas
Gravel and rounded pebbles: Frequent in areas with constant flow
Larger stones and boulders: Interspersed along margins, especially where tree roots stabilize banks
Organics: Silt, decaying leaves (from riparian species like alders and figs), scattered alder cones, and occasional fig leaves
Calcium carbonate precipitates: Sometimes visible due to lime-rich springs
Hardscape/Structure
Banks densely rooted by riparian trees: Roots penetrate into the water, offering substrate complexity and shelter
Occasional woody debris: Driftwood mainly from flooding or overhanging branches
Emergent and floating vegetation: Provides cover and structure
Visible bedrock in places: Exposed by strong water movement
These elements create a habitat with abundant crevices, overhangs, and shade, while open substrates allow for schooling and foraging.
Aquatic Vegetation and Algae
Although plant diversity is limited in the wild relative to some tropical rivers, the following dominate:
Ceratophyllum demersum (hornwort): Most widespread submersed plant
Potamogeton spp. (pondweeds): Broad-leaved species in slower currents
Eichhornia crassipes (water hyacinth): Floating, particularly in less-moving backwaters
Fissidens fontanus (aquatic moss): Found attached to rocks and roots
Najas guadalupensis: In some localities, especially with slower flow
Spirogyra and other filamentous green algae: Thriving in full sun, particularly on substrates, roots, and rocks
Ulotrichales, Zygnematales, Oedogoniales (orders of filamentous algae): Primary food resource for Ameca splendens
Habitat Community: Coexisting Species
Extensive fieldwork and publication review reveal the following tables of fish, aquatic plants, and invertebrates sharing the Ameca splendens biotope, primarily from upper Río Teuchitlán and comparable habitats.
Fish Species Table
Species Name | Family | Status | Notes |
|---|---|---|---|
Goodea atripinnis | Goodeidae | Native, widespread | Blackfin Goodea; dominant cohabitant |
Xiphophorus hellerii | Poeciliidae | Introduced/Native? | Green Swordtail; sometimes abundant |
Poecilia mexicana | Poeciliidae | Invasive | Atlantic Molly; displaces natives in polluted sites |
Pseudoxiphophorus bimaculatus | Poeciliidae | Invasive | Two-spot Livebearer; competitive, critical threat |
Oreochromis aureus | Cichlidae | Invasive | Blue Tilapia; major contributor to decline |
Zoogoneticus purhepechus | Goodeidae | Native, at risk | Purépecha Splitfin; upper reaches |
Zoogoneticus tequila | Goodeidae | Endangered/native | Reintroduced; limited range |
Notropis amecae | Cyprinidae | Extinct/introduced | Ameca Shiner; rare, under restoration |
Ictalurus dugesi | Ictaluridae | Native | Mexican Catfish; present in some reaches |
Allotoca goslinei | Goodeidae | Extinct in wild | Banded Allotoca; part of restoration programs |
Skiffia francesae | Goodeidae | Extinct in wild | Golden Skiffia; found in historic periods |
Lepomis macrochirus | Centrarchidae | Invasive | Bluegill; recent, rare in upper springs |
Aquatic Plant Species Table
Species Name | Plant Group | Wild Distribution in Biotope |
|---|---|---|
Ceratophyllum demersum | Submerged plant | Abundant throughout |
Potamogeton spp. | Emergent | Patches in slow pools |
Fissidens fontanus | Aquatic moss | On rocks, driftwood, and roots |
Eichhornia crassipes | Floating plant | Shaded, less turbulent waters |
Najas guadalupensis | Submerged plant | Select slow-flowing reaches |
Pistia stratiotes | Floating | Scattered, especially in pools |
Spirogyra sp. | Filamentous algae | Mats on substrate and obstacle |
Ulotrichales/Zygnematales/Oedogoniales | Filamentous algae | Main algal forage on wood/rock |
Invertebrate Species Table
Species Name/Group | Type | Distribution and Notes |
|---|---|---|
Chironomidae larvae | Aquatic insect | Common in all sediment and algae |
Oligochaete worms | Worms | Present in organic detritus |
Copepods | Zooplankton | Numerous, in open water and on plants |
Mosquito larvae | Insect larvae | Especially in stagnant pools |
Aquatic snails (Physidae/Planorbidae) | Gastropod | Locally abundant on vegetation |
Ephemeroptera nymphs | Mayfly nymphs | In clean, oxygenated runs |
The complex co-occurrence of native goodeids and introduced poeciliids and cichlids underscores the habitat’s ecological fragility. In pristine spring runs (e.g., El Rincón), Ameca splendens coexists peacefully with Goodea atripinnis and, where reintroduced, Zoogoneticus tequila and N. amecae. However, in disturbed zones, invasives (Oreochromis, Poecilia) and competitors (Pseudoxiphophorus) often dominate and threaten the survival of natives, emphasizing the importance of biotope fidelity in conservation aquaria.
Replicating the Wild Habitat in the Aquarium
Substrate Choices
To authentically mirror their native environment, use a substrate combination that blends:
Fine sand (white or beige, 0.5–1 mm grain): To match silt and sand of natural springs
Rounded gravel and small pebbles (5–20 mm): Interspersed throughout tank base
Scattered flat stones, larger river rocks, and boulders: Create crevices and hideouts
Leaf litter (dried alder or fig leaves) and alder cones: Subtle, targeted addition for aesthetics and botanicals
No sharp gravel or dark “artificial” substrates: These are out-of-place for the Ameca biotope.
Hardscape Elements and Aquascaping
Layout should focus on:
Dense root tangles: Artificially recreate with inert driftwood or securely planted terrestrial roots
Stacked rocks: Use to form open shelters, sight breaks, and encourage dynamic flow
Driftwood/found branches: Erodes slowly; supports aufwuchs/algae growth for foraging
Minimal open sandy area: Mimics backwater and foraging zones
Edge plantings: Hornwort, pondweed, or floating plants—secured to avoid uprooting from boisterous fish
Best practices for assembling the hardscape:
Ensure all rocks/wood are scrubbed, boiled, or prepared to avoid contamination.
Anchor plants into substrate using weights or plant pots.
Arrange for open swimming lanes (Butterfly Goodeid is active and social), with 30–50% cover for refuge, particularly for subordinate or gravid individuals.
Water Conditions and Maintenance
Temperature: Target 22–26°C year-round, with short "cooling" winter period (15–20°C) if breeding fidelity is desired
pH: Maintain 7.4–8.2 (alkaline is better)
Hardness (GH): ≥12°dGH, with a preference for mineral-rich sources
TDS: 180–320 ppm (adjust upward for especially hard local tap waters)
Filtration: Use efficient external canister or large sponge filters; moderate to high turnover
Aeration: Vigorous; splashing returns or airstones are recommended
Flow: Provide moderate continuous flow; ensure dead spots are minimal but allow some slack waters for fry
Lighting: Bright, full-spectrum; use strong LEDs or intense T5/T8 fluorescents to promote algae/hornwort growth
Water changes: Large (40–60%) weekly, aged and remineralized water; avoid rapid swings in chemistry or temperature.
Aquascaping Techniques for the Ameca Biotope
Prioritize natural clusters of plants (hornwort, pondweed), breaking vertical line-of-sight.
Leave open swimming space, especially front and mid-tank.
Avoid decorative ornaments, colored gravels, or unnatural decor; biotope accuracy supports natural behaviors and health.
Regularly allow some on-surfaces algae accumulation—Ameca splendens actively grazes this and benefits nutritionally.
Breeding Biology and Protocols
Natural Reproductive Strategies
Ameca splendens exhibits advanced livebearing—embryos develop internally for about 55–60 days. Unique among common aquarium livebearers, their developing fry are nourished directly by the mother via a trophotaenia, a structure analogous to a mammalian placenta. Young are born exceptionally large—up to 18–22 mm—and robust, rendering them largely immune to parental predation. Breeding occurs year-round in warm springs, with two annual peaks observed in natural environments: spring and late fall.
Reproductive cycle highlights:
Males display courtship (vertical head-stands, body shaking)
Females initiate spawning by quivering in front of males
Mating is brief; males introduce sperm via a flexible andropodium
Superfetation (embryos of multiple ages present in one female) occasionally observed
Females cannot store sperm for future broods (unlike guppies)
Detailed Aquarium Breeding Guidelines
Colony vs. Selective Breeding Approaches:
Colony Method: 8–15 adults in a single well-structured 75–100 liter tank; fry are large enough to avoid predation, so youth congregations build rapidly
Selective or Pair Breeding: Individual pairs in minimum 40–60 liter tanks, or secluded “maternity” tanks for about-to-drop females
Best Practices:
Maintain a higher ratio of females (2–3:1) to males to diffuse aggression and reduce male-bullying during courtship
Include dense vegetation (e.g., hornwort rafts or moss balls) for fry refuge
Keep temperature in the breeding tank at 21–24°C for optimal results; raising above 27°C shortens gestation but may reduce fry vigor and adult longevity
Gestation and Fry:
Gestation: 50–60 days; variable with temperature
Brood size: 10–30, occasionally up to 40 for large females
Fry: Born with attached trophotaenia (remnant "umbilical cord")—disappears within 48–72 hours
Fry require no parents’ removal; high-protein first foods (micro-pellets, newly hatched artemia) and frequent small water changes boost growth.
Breeding Cycle Modulation: For robust long-term health and strong fry, it is recommended to provide a brief winter “rest” by lowering tank temperature to 17–20°C for 2–3 months, reducing or pausing reproduction as observed in the wild.
Diet and Feeding Regimen
Wild Diet
In its native habitat, Ameca splendens is primarily a grazer of filamentous algae and associated aufwuchs. Gut content analyses and field reports reveal their omnivory is slightly biased toward:
Filamentous green algae (Ulotrichales, Zygnematales, Oedogoniales)
Diatoms
Aufwuchs micro-organisms: Small invertebrates, detritus
Occasional prey: Mosquito larvae, copepods, oligochaete worms, terrestrial insects
This fiber-rich diet is essential for their health—rapid gut transit times and specialized teeth support continuous grazing.
Feeding in Captivity
Key Elements:
Staple Foods: High-quality spirulina flake, algae-based wafers, blanched vegetables (spinach, lettuce, peas, zucchini)
Protein Supplements: Live or frozen daphnia, bloodworms, tubifex, whiteworms, newly hatched brine shrimp; particularly vital for fry and conditioning breeders
Algae Maintenance: Encourage some algae growth in tank for continual grazing
Avoid: Over-reliance on high-protein carnivore foods (e.g., exclusive bloodworm diets) or low-fiber commercial foods; these can cause digestive problems and obesity
Duckweed, hornwort, and soft greens: Will be eaten, but robust/fiber-rich plants should be prioritized for aquascaping to avoid excessive destruction.
Feed small amounts multiple times per day and remove our uneaten food. Periodic fasting days are also beneficial for digestive health.
Compatible Tankmates and Community Dynamics
General Guidelines
Ameca splendens is semi-aggressive and boisterous, and their social structure is hierarchical—an alpha male will emerge and establish a pecking order through threat displays and occasional nipping (especially among males). Fin-nipping is a noted behavior, particularly targeting long-finned or slow-moving species.
Best Practices for Tank Community:
Best Option: Species tank of 8–15 individuals (preferably more females)
Alternative Community Candidates:
Other robust, fast-swimming livebearers (e.g., Goodea atripinnis, Zoogoneticus tequila)
Some native catfish (Ictalurus dugesi) if space permits
Certain Central American barbs or cichlids (only in very large aquaria)
Avoid: Small, delicate, long-finned, or slow-moving fish (e.g., fancy guppies, most tetras)
Space: Overcrowding amplifies aggression; provide at least 60 liters per group of 8 adults
Visual Barriers: Structure tank to allow subordinate fish refuge; use rocks, plants, wood, moss balls
Note: Even in communities, provision of sufficient cover and observation for long-term interactions is vital. Remove any tankmates that show chronic signs of stress or damage.
Observed Wild Communities
In their last wild strongholds, Ameca splendens flourished with Goodea atripinnis, Xiphophorus hellerii (green swordtail, sometimes considered introduced), and a shifting cast of threatened or extinct regional goodeids. The invasion of Oreochromis (tilapia), Poecilia mexicana, and Pseudoxiphophorus bimaculatus coincided with local extirpation events—do not combine with these aggressive or highly competitive species in aquariums designed for conservation breeding.
Special Challenges and Conservation Importance
Challenges:
Water Quality: Butterfly Goodeids are moderately tolerant, but best color, vigor, and reproductive output come with fastidious water change and filtration regimens.
Aggressive Nature: As described, not a good "general" community fish; their nipping and active swimming style overwhelm gentle tankmates.
Plant Eating: They may destroy soft-leaved plants; select tough or rapidly growing species.
Population Control: High fry survival can result in overcrowding unless actively managed.
Captive Ameca splendens populations are now regarded as genetic reservoirs for future reintroductions or reinforcement of remnant wild populations. Thus, aquarium care is not just a hobby but part of a broader global conservation strategy. Breeders are encouraged to maintain accurate husbandry records, retain any known lineage information, and collaborate with conservation bodies or species preservation projects as possible.
Conclusion
Replicating the wild environment of Ameca splendens in the aquarium is not only a matter of aesthetic or behavioral fidelity, but sits at the intersection of hobby practice, education, and conservation. By carefully reconstructing the substrate, hardscape, water chemistry, and community composition documented from the Río Teuchitlán, committed aquarists can maintain robust, genetically healthy captive populations and contribute to the restoration of a critically imperiled icon of Mexican aquatic biodiversity.
For those seeking to join or support conservation breeding programs, accurate record keeping, periodic water parameter monitoring, and willingness to collaborate with broader ex-situ recovery initiatives are encouraged. Finally, showcasing well-constructed biotope aquaria for public viewing, online streaming, or educational display can help raise awareness for the ongoing struggle to preserve Mexico’s endemic freshwater fauna in the face of accelerating anthropogenic pressures.
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