TankBud

San Marcos goodeid

Xenotoca doadrioi

Also known as Doadrio's splitfin, Redtail goodeid San Marcos

FreshwaterFish

San Marcos goodeid (Xenotoca doadrioi)
Andrew Bogott · CC BY-SA 4.0

Care at a glance

Temperature
64–79°F
18–26°C
pH
7.0–8.2
Adult size
2 in
5 cm
Minimum tank
20 gal
75 L
Temperament
Peaceful
Social behavior
Social
Tankmates
With caution
Swim level
Middle
Difficulty
Medium
Breeding
Livebearer · Medium
Rarity
Rare
Family
Goodeidae
Origin
San Marcos springs, Jalisco, Mexico

Overview

The San Marcos goodeid is a hardy, active livebearer for the middle of a cool, unheated tank. It suits a keeper with a little experience.

Did you know

Like other goodeids, the San Marcos goodeid feeds its unborn young through trophotaeniae, ribbon-like cords that work like a placenta. The cords trail from the belly at birth. It is a mammal-style connection, built independently by a small Mexican fish.

Caring for the San Marcos goodeid

Keep San Marcos goodeids as a colony, with a good share of females to spread out the males' attention. A tank of 20 gal (75 L) or more suits the colony. They swim in the middle of the tank.

Give them clean, moderately hard and alkaline water, moving with good current and filtration. Hold it at 64 to 79°F (18 to 26°C) and a pH of 7.0 to 8.2, stable and on the cooler side. This fish does not need heat or want tropical warmth. Generous water changes keep it in condition.

It grazes plant matter in the wild, so include vegetable and spirulina foods alongside regular flake and small frozen foods. San Marcos goodeids are generally peaceful, but males can be nippy and pushy. Keep them in a species tank, or pick robust companions with short fins.

Males are slate-bodied with an orange tail band. The San Marcos goodeid is a livebearer with a gestation of roughly seven to eight weeks. Females give birth to a modest brood of well-developed young, and breeding is of moderate difficulty.

Good to know

The San Marcos goodeid, Xenotoca doadrioi, is a splitfin in the family Goodeidae. It was split from Xenotoca eiseni as its own species in 2016. It is now critically endangered in its shrinking Jalisco springs.

In the wild

The San Marcos goodeid comes from a small spring-fed system at San Marcos, in Jalisco, Mexico. Its home water is cool, hard and moving.

Common questions

What size tank does a San Marcos goodeid need?

A San Marcos goodeid needs at least 20 gal (75 L). It spends most of its time in the middle.

What temperature and pH does a San Marcos goodeid need?

A San Marcos goodeid is comfortable at 64–79°F (18–26°C) with a pH of 7.0–8.2.

What does a San Marcos goodeid eat?

A San Marcos goodeid eats regular flake and small frozen foods, plus vegetable and spirulina foods. It grazes plant matter in the wild.

How big does a San Marcos goodeid get?

An adult San Marcos goodeid reaches about 2 in (5 cm).

How can you tell a male San Marcos goodeid from a female?

Males are slate-bodied with an orange tail band.

How does a San Marcos goodeid breed?

San Marcos goodeids are livebearers with a gestation of roughly seven to eight weeks. A female gives birth to a modest brood of well-developed young, and breeding is of moderate difficulty.

Related species