Redtail Splitfin

Redtail Splitfin (Xenotoca eiseni)

AKA: Redtail Goodeid

A colorful and interesting livebearing goodeid from west-central Mexico. Known as the “Redtail Splitfin” or “Redtail Goodeid,” this species is prized for the bright red-orange tail and tail-base of adult males and the hump that develops behind the head in older males. It is one of the more popular goodeids in the aquarium hobby and remains an important species for captive breeding programs given its Endangered status in the wild.

Key Features

• Maximum Size: Up to 7 cm / ~2.8 inches TL (females slightly larger than males).
• Appearance: Deep-bodied fish with a distinctive red-orange tail and tail-base in adult males. The upper body and head are olive-brownish to dusky, while the throat and belly are yellowish to whitish. Females are more plainly colored and generally slightly larger. Older males develop a noticeable hump behind the head.
• Fin Details: Males have a larger dorsal fin and the characteristic goodeid splitfin (notch in the anal fin).

Aquarium Care

• Tank Size: Minimum 30–40 gallons for a small group or pair (larger is better).
• Water Parameters: Cool to warm freshwater; 59–86°F (15–30°C), pH 7.0–8.5, moderate to hard. Excellent water quality with regular partial changes is important. Provide a well-structured tank with rocks, plants, and hiding spots. A winter cooling period can help regulate breeding.
• Diet: Omnivorous — accepts a wide range of foods including flakes, pellets, frozen foods, and live foods (insects, worms, small crustaceans). Some vegetable matter is beneficial.
• Behavior: Generally peaceful but can be territorial, especially during breeding. Best kept in groups or as a pair with ample cover. Live-bearing with trophotaeniae (nutrient-providing structures like an umbilical cord). Females give birth to 10–50 relatively large fry every couple of months. Fry survival is good with sufficient cover and food.

IUCN Status Endangered (EN)