Black-Band Fighting Gaucho (Cynopoecilus melanotaenia)

Overview

Black-Band Fighting Gaucho is the supplier trade name for a small South American annual killifish now best presented as Cynopoecilus melanotaenia. The older name Cynolebias melanotaenia is still useful because it appears in supplier data, older hobby material and search behaviour, but FishBase treats that name as the original combination and a synonym rather than the current accepted name.

This is not a routine warm community fish. It is a specialist annual killifish from seasonal pools and wetlands in southern Brazil and Uruguay, the kind of habitat that fills, matures and dries on a cycle. The fish supplied on this SKU are listed by Petra at 2.5-5 cm. FishBase gives males a maximum of 4.3 cm standard length and females about 3.5 cm standard length, so plan for a compact fish with strong behaviour rather than a large display species.

Quick Facts

• Current name: Cynopoecilus melanotaenia
• Supplier / older name: Cynolebias melanotaenia
• Trade names: Black-Band Fighting Gaucho, Fighting Gaucho
• Supplied size: 2.5-5 cm
• Adult planning size: around 4-5 cm total length
• Temperature: 18-24 C, with 20-23 C a sensible aquarium target
• pH: 6.0-7.5
• Hardness: soft to lightly mineralised, about 2-10 dGH
• Best setup: covered 40 L+ species aquarium
• Diet: small live and frozen foods

Identity and Source Notes

FishBase lists Cynopoecilus melanotaenia as the current accepted species and places it in Brazil and Uruguay. Its synonym detail page shows Cynolebias melanotaenia as the original name, not the current accepted one. That is why the product title has been cleaned: customers still see the familiar Black-Band Fighting Gaucho wording, but the scientific field, care facts and source notes now use the current name.

The genus is part of a group of inseminating seasonal killifish associated with temporary pools in southern Brazil and adjacent Uruguay. Killifische.info and the Biodiversity Data Journal material on the Cynopoecilus melanotaenia complex both describe this southern Brazil / northeastern Uruguay context. For aquarium care, that matters more than any generic tropical-fish label: keep the tank cool to moderate, quiet, covered and arranged around seasonal-killifish behaviour.

Appearance

The exact Petra source image for this SKU shows a slim annual killifish with a dark blue-black lateral band, pale blue spotting, orange to red edging on the dorsal and caudal fins, and a soft golden-green body sheen. That real reference photo has been added to the gallery as an extra image. The gallery images are supporting aquarium-scene views, but the source photo is the best visual anchor for what this SKU actually represents.

Males are the more decorative fish, especially when settled and displaying. Females are smaller and plainer, which is normal for many annual killifish. A dark base, floating cover and side planting help the stripe and fin edges show without forcing the fish into bright exposed water. In a bare, busy or over-lit tank, the same fish can look washed out and nervous.

Aquarium Setup

Use a secure lid. Small killifish jump, and an uncovered aquarium is a needless risk. A 40 litre aquarium is a sensible minimum for a pair or small group, with gentle filtration, low flow and plenty of cover. This species suits a quiet specialist setup more than a busy mixed display.

Fine sand, leaf litter, Java moss, floating plants and a removable peat-fibre or coco-coir spawning container all work well. The spawning medium should be soft enough for natural bottom-spawning behaviour and easy to remove if you intend to incubate eggs. Avoid sharp gravel, strong current and large open territories that leave weaker fish exposed.

Feeding

Feed small live and frozen foods. Daphnia, cyclops, baby brine shrimp, mosquito larvae, grindal worm and finely chopped bloodworm are all better staples than relying on dry food alone. Fine prepared foods may be taken once the fish are settled, but live and frozen foods are what usually bring out colour, condition and breeding behaviour.

Offer small portions and remove leftovers. Annual killifish need regular feeding, but dirty water punishes them quickly. A light, steady feeding rhythm with clean water and calm cover will do more for this fish than heavy meals in a tank where waste collects in the substrate.

Behaviour and Compatibility

The Black-Band Fighting Gaucho is best treated as a species-aquarium fish. Males can display and defend space, especially around spawning media, while the species is small enough to be outcompeted by faster community fish. The old FAQ made community keeping sound too easy; the better advice is to keep it by itself unless the keeper is deliberately managing a calm, compatible specialist setup.

Avoid large fish, fast feeders, fin-nippers, hot hard-water community setups and ornamental shrimp you would be upset to lose. If tank mates are attempted, they should be tiny, calm fish with similar cool, soft-water requirements, and breeding should not be the goal. For most customers, a covered species aquarium gives better feeding control, stronger colour and less stress.

Breeding

This is an annual bottom-spawning killifish. In nature, seasonal pools allow rapid growth and spawning, then eggs survive the dry phase in the substrate. FishBase notes bottom spawning and a short incubation figure for the species, while the wider Cynopoecilus literature treats the group as seasonal and internally inseminating. In practice, aquarium breeding is a specialist project, not a casual community-tank event.

Condition fish with live and frozen foods, provide peat fibre or coco coir, then remove and store the medium damp rather than wet according to annual-killifish breeder practice. Fry need very small live foods at first. This is exactly the kind of life cycle that makes annual killifish fascinating, but it rewards patient keepers who are comfortable with careful egg handling.

Common Mistakes

• Using only the old Cynolebias melanotaenia name and missing the current Cynopoecilus melanotaenia taxonomy.
• Keeping the fish too warm because it appears in a tropical-fish catalogue.
• Putting it into a robust community aquarium where it cannot feed or spawn naturally.
• Skipping the lid.
• Using no soft spawning medium for a fish built around seasonal substrate spawning.
• Expecting a long-lived display fish rather than a short-lived annual species.

Related Killifish

If you are comparing specialist South American annual killifish, also look at Black Pearlfish, White's Cynolebias / Rio Pearlfish, Featherfin Pearlfish and Ladiges' Gaucho.

Delivery and Guarantee

When this fish is in stock, it is packed for livestock transport through our licensed live-animal courier process. The important promise is straightforward: careful packing, temperature-aware dispatch planning and our Live Arrival Guarantee.

Sources Checked

Care and identity notes were checked against FishBase for Cynopoecilus melanotaenia, FishBase synonym detail for Cynolebias melanotaenia, Killifische.info, Biodiversity Data Journal material on the Cynopoecilus melanotaenia complex and Petra supplier media/data.