At a glance the quick version
Males are the smaller sex at about 7-8 cm; females reach about 10-12 cm (FishBase gives 12 cm TL for females, Seriously Fish 9 cm SL)
Looks how to spot one
Scaled, deep-bodied livebearer
A sturdy, deep-bodied fish. Males sparkle with scattered metallic scales and carry a dark tail fin finished with a bright yellow edge band. Females are plainer, silvery-olive with dark spots along the sides.13
Personality what they are like
A lively, confident fish. Males sort out a pecking order among themselves and can be pushy, so it suits a species tank or a group of robust, similar-sized tankmates rather than a calm community of delicate fish.13
Daily activity how busy a day looks
A strong, active swimmer that uses the whole tank, so give it a roomy aquarium with open swimming space.3
Grooming and care the hands-on bits
Keep the water clean and well oxygenated. It prefers neutral to hard, alkaline water and dislikes very soft, acidic conditions. Plenty of vegetable matter in the diet keeps it in top shape.13
Home where they are happiest
Minimum tank base about 90 x 30 cm (around 80 litres). Temperature about 21-24 °C in aquarium sources (FishBase lists 26-32 °C), pH 7.0-8.0, hardness about 10-20 dGH. Floating plants give newborn fry cover.123
Food basics what goes in the bowl
Omnivore with a strong taste for greens. Offer a mix of flakes or pellets, spirulina or algae-based foods, blanched vegetables such as spinach, and small frozen or live foods.13
Company who they like around
Best kept as a group with several of each sex, or as a single pair. Spreading male attention across more females keeps things calmer.13
The story where it all began
Miller and Fitzsimons described the species in 1971 from the Ameca river system in Jalisco. Its tiny native range has shrunk greatly, and strong captive populations kept by aquarists help keep the species going.23
Fun facts for the dinner table
- 1
Developing young are fed inside the mother through ribbon-like structures called trophotaeniae, which work much like a placenta.1
- 2
Pregnancy lasts about 55-60 days and produces roughly 5-30 large fry.1
- 3
Newborn fry can measure around 2 cm and stay silvery for their first couple of weeks.3
- 4
A lower-ranking male shakes its head as a calming signal to a dominant one.3
- 5
Its genus name comes from the Ameca river in western Mexico.2
Recognised by the official bits
- IUCN Red List
- Critically Endangered (assessed April 2018); small wild populations remain in a few springs and streams2
- Taxonomy
- Family Goodeidae (splitfins); described by Miller & Fitzsimons in 19712
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Butterfly Splitfin. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- Seriously Fish: Ameca splendens (Butterfly Goodeid) seriouslyfish.comused for range, size, tank size, water parameters, diet, behaviour, dimorphism, breeding
- FishBase: Ameca splendens, Butterfly splitfin fishbase.seused for author and year, distribution, max length by sex, environment, IUCN status, etymology
- Wikipedia: Butterfly splitfin en.wikipedia.orgused for other names, description, size, conservation history, aquarium notes, diet, behaviour facts
Checked 2026-09-30. Text is written in our own words from these sources.