Redtail Splitfin Care Guide - Aquarium Setup, Diet & Breeding

The Redtail Splitfin is a relatively uncommon Mexican goodeid with a sturdy, laterally compressed body and a distinctive reddish to orange tail. Its base colour can range from olive and bronze to greyish brown, often with subtle dark markings that become more pronounced when the fish is settled and displaying. Males are generally smaller and more vividly marked than females.

These are active, alert fish with plenty of personality. They spend much of their time in the middle and upper levels of the aquarium, investigating their surroundings and interacting with one another. Males may spar and display, but serious damage is usually avoidable when the group is sensibly balanced and has enough space.

In the wild, Redtail Splitfins inhabit clear to moderately turbid streams and pools in a warm Mexican drainage. Their habitat is shaped by seasonal changes in flow, with rocks, submerged vegetation and marginal plants providing shelter and feeding surfaces.

Xenotoca doadrioi has a very limited distribution and is not a routine mass-market aquarium fish. Captive-kept individuals are therefore especially valuable, and obtaining them from reputable, legally operating breeders helps reduce pressure on wild populations while supporting the preservation of this unusual livebearer.

Redtail Splitfins are endemic to the upper Río Tamazula, part of the Río Coahuayana drainage in Jalisco, western Mexico. Their restricted natural range makes them an important species for responsible captive conservation and careful aquarium management.

A group should be given at least 80 litres, with a larger aquarium preferable for a mixed-sex colony or community. Aim for a footprint of roughly 90 × 30 cm or more rather than relying on height alone. Use a sturdy filter with good oxygenation, open swimming space and a secure lid, together with rounded rocks, driftwood, hardy plants and dense cover around the edges. A fine gravel or sand substrate is suitable, and moderately hard, alkaline water is generally appropriate for this mineral-rich stream fish.

Females can reach about 7 cm (2.8 in), while males usually remain closer to 5–6 cm (2.0–2.4 in).

Offer a varied omnivorous diet built around quality flakes or small pellets, supplemented with blanched spinach, peas, spirulina-based foods and soft algae growth. They also appreciate frozen or live foods such as daphnia, brine shrimp, bloodworm and mosquito larvae. Vegetable matter is particularly useful because wild goodeids commonly graze algae and aufwuchs while taking small invertebrates opportunistically.

Redtail Splitfins can work in a peaceful, spacious community containing robust livebearers and other hard-water species, such as platies, swordtails, mollies, larger peaceful goodeids and suitable rainbowfish. Avoid delicate, slow-moving or long-finned fish, as this active species can become boisterous and may nip fins. They should not be housed with highly aggressive fish, cool-water specialists with very different requirements, or small timid species that will be outcompeted at feeding time.

Redtail Splitfins are livebearers that reproduce through internal fertilisation. Keep a healthy group with several females per male, and provide plenty of fine-leaved plants or spawning mops for cover. Pregnancy usually lasts several weeks, after which the female releases relatively large, fully formed fry. Adults may prey on newborns, so dense cover or a separate rearing area improves survival. The young accept newly hatched brine shrimp, finely powdered foods and other small, nutritious fare.

Females are larger and deeper-bodied, particularly when carrying developing young. Males are smaller and more slender, with a more noticeable gonopodium and often stronger red or orange colour in the tail and rear of the body.