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Redtail Splitfin

Xenotoca eiseni

Also called Redtail goodeid, Mexcalpique cola roja

SpeciesShort profile

From West-central Mexico: the Río Grande de Santiago basin and waters near Compostela, Nayarit.12

At a glance the quick version

Length6 to 7 cm213
Sizesmall
Hardy
Striking red-orange tail on males
Tolerant of a wide temperature range
31

Looks how to spot one

Scaled goodeid livebearer

A sturdy, deep-bodied livebearer. Males develop a raised hump behind the head that grows with age and use a notched anal fin (andropodium) for mating.13

ColoursOlive-brown backBlue-black band along the side (males)Red-orange tail and tail base (males)Yellowish-white bellyPlainer females13

Personality what they are like

Character varies between individuals: some live calmly in a community, while others nip fins. Keeping them in a group or a species tank works best.31

Daily activity how busy a day looks

Active and bottom-to-midwater swimming; appreciates room to move.32

Grooming and care the hands-on bits

Undemanding and hardy. Include plenty of vegetable food and keep the water clean.13

Home where they are happiest

Aquarium from about 60 x 30 x 30 cm (around 54 litres). Water 15-30 °C, pH 6.0-8.0, 10-20 dGH; harder, alkaline water preferred.312

Food basics what goes in the bowl

Unfussy omnivore that needs vegetable matter in the diet alongside flake and frozen foods.13

Company who they like around

Best in a group of its own kind or a species tank; avoid slow, long-finned tankmates.31

The story where it all began

Rutter described the species in 1896 and named it after Gustav Eisen, curator of marine invertebrates at the California Academy of Sciences. It is one of the best-known goodeids in the aquarium hobby.12

Fun facts for the dinner table

  1. 1

    Mothers feed developing young through ribbon-like trophotaeniae, which work much like an umbilical cord.1

  2. 2

    Fry are about 15 mm long at birth, large for a livebearer.1

  3. 3

    Wild fish tend to pair with mates of similar size.1

  4. 4

    Females give birth roughly every two months.2

Recognised by the official bits

IUCN Red List
Endangered (assessed 2018)2
Taxonomy
Family Goodeidae; described by Rutter in 18961

The care rhythm a typical week and year

A typical home-care rhythm for a Redtail Splitfin. A starting point, not a vet's advice.

Owner questions the things everyone asks

How often should I feed my Redtail Splitfin?

Furry Diary's starting plan is to feed small amounts once or twice a day. This matches their unfussy omnivore nature, but always check the food label and ask your vet for exact portions.31 Pet Wiki plan

What does a Redtail Splitfin eat, and what should it never eat?

They are unfussy omnivores that need vegetable matter alongside flake and frozen foods. Never feed them anything that could harm them, like large or sharp items; ask your vet for a safe list.31

How much space does a Redtail Splitfin need?

They need an aquarium from about 60 x 30 x 30 cm (around 54 litres). This gives them room to swim actively in the bottom to midwater.312

What temperature, light or water does a Redtail Splitfin need?

Water should be 15-30 °C, pH 6.0-8.0, and 10-20 dGH, with harder, alkaline water preferred. Furry Diary suggests checking temperature daily and testing water weekly.312 Pet Wiki plan

How often should I clean a Redtail Splitfin's home?

Furry Diary's plan is to change about 25% of the water weekly, clean the glass weekly, and rinse the filter in old tank water monthly. Keep the water clean for their health. Pet Wiki plan

Can a Redtail Splitfin live with others?

Yes, they are best in a group of their own kind or a species tank. Avoid slow, long-finned tankmates as some individuals may nip fins.31

How long does a Redtail Splitfin live?

Lifespan varies depending on care and environment. For specific details, ask a good breeder or an exotic-pet vet.

Can I handle a Redtail Splitfin?

It's best not to handle them as they are delicate fish. They are active swimmers that appreciate room to move, so enjoy watching them instead.32

Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.

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Where this comes from

Every fact on this page has a numbered source. Spotted an error? support@petwiki.app.

  1. Wikipedia: Xenotoca eiseni en.wikipedia.orgused for range, colour, history, facts
  2. FishBase: Xenotoca eiseni fishbase.seused for size, environment, IUCN, reproduction
  3. Seriously Fish: Xenotoca eiseni seriouslyfish.comused for tank size, water, behaviour

Checked 2026-09-30. Text is written in our own words from these sources.