Red-Tailed Goodeid (Xenotoca eiseni)

Overview

Red-Tailed Goodeid (Xenotoca eiseni) is a specialist Mexican goodeid also known as the Redtail Splitfin or Orange-tailed Goodeid. It is a livebearing fish, but it should not be treated like a soft community guppy or a standard mixed livebearer. This is an active, robust splitfin for aquarists who can provide hard, alkaline water, open swimming room, high water quality and a group large enough to spread male attention and occasional fin-nipping.

Current Shopify variants cover 2-2.5 cm juveniles, 3.5-4.5 cm young fish and 5-7 cm larger fish, but live stock changes with supplier availability.

Why Keep Red-Tailed Goodeids?

Xenotoca eiseni has a very different feel from common poeciliid livebearers. Mature males develop the red-orange tail and caudal-peduncle colour that gives the species its common name, while females are plainer, deeper-bodied and often slightly larger. A settled group is busy, bold at feeding time and constantly interacting, which makes the species rewarding in a dedicated hard-water aquarium.

This is also a fish with real conservation interest. FishBase lists the species as Endangered, and goodeid specialists highlight that true Redtail Splitfin populations should not be casually mixed with similar-looking redtail goodeids from other locations. In the aquarium, that means keeping the species name and any supplier lineage information accurate and avoiding hybridising with other goodeids.

Water Parameters

Red-Tailed Goodeids are adaptable, but they are at their best in clean, mineral-rich water. Avoid soft, acidic conditions and avoid warm, stale tanks. They appreciate oxygen, regular water changes and stable chemistry more than decorative complexity.

Tank Size and Layout

For a small group, plan more floor space than a typical nano livebearer setup. A mature aquarium from about 100 litres can work for a modest group if the layout is open and well filtered, while larger groups and breeding colonies deserve substantially more room. Goodeid Working Group husbandry notes are more conservative and recommend very spacious, broad tanks for serious long-term colonies.

Use open swimming space through the front and middle, with robust planting, roots or rocks at the sides and back. Floating plants can calm the fish, but do not pack the whole tank with delicate stems. These fish may browse algae and aufwuchs and can damage very soft plants, so choose hardy planting and accept that a goodeid aquarium can look more natural and rugged than manicured.

Compatibility

Red-Tailed Goodeids are best kept in a species group or with fast, short-finned fish that enjoy similar hard-water conditions. They are not ideal companions for slow fancy guppies, long-finned bettas, delicate dwarf gouramis or tiny soft-water fish. The safest approach is to keep a group of their own kind, with more females than males where sexing is possible, and enough cover that no single fish is constantly chased.

Feeding

This species is an unfussy omnivore, but it should not live only on rich frozen foods. Offer a varied diet with quality flake or granule, algae wafers, vegetable-rich foods, and small frozen foods such as daphnia, brineshrimp, mosquito larvae or bloodworm. Vegetable matter is important for condition and digestion, especially in mature groups that spend the day grazing surfaces.

Feed small portions that are eaten quickly. A confident group will rush food, so spread food across the surface and midwater to reduce competition. If you are conditioning adults for breeding, raise the quality of food and water together rather than simply feeding more.

Breeding and Fry

Goodeids are livebearers, but they breed differently from guppies and swordtails. Males use a modified anal fin called an andropodium, and developing young are nourished by structures called trophotaeniae. Females can produce sizeable fry roughly every two months when conditions are good, and newborn fry are much larger than typical guppy fry.

Adults may eat some fry, especially in bare tanks. Dense cover, floating plants, mossy areas or a separate rearing space improve survival. If conservation-style breeding matters to you, keep accurate labels and avoid mixing unknown Redtail Splitfin lines.

Current Stock and Ordering Notes

When stock is available, the product may appear in juvenile and larger size options. Use the size selector and live stock state on the product page as the final truth before checkout.

First-time customers can use the active WELCOME10 code for 10% off eligible first orders. Live fish orders are packed for licensed live-animal courier service and supported by the Tropical Fish Co Live Arrival Guarantee, with dispatch timing chosen around animal welfare and suitable weather.

Best For

Related Goodeids and Livebearers

If you are comparing specialist livebearers, also check Barred Splitfin, Alien Splitfin, Spotted Skiffia, Twoline Skiffia and the wider livebearer collection. These links help compare temperament, water hardness and group behaviour before choosing tank mates.

Sources Used for Care Checks

Care and identity were checked against FishBase, Goodeid Working Group husbandry notes, and UK retailer species notes from Maidenhead Aquatics / Fishkeeper. Supplier data was used for the current Petra size options, pH, hardness, temperature and source photo.