Feather-Fin Pearl Fish (Cynolebias constanciae) — 2,5-5cm

Overview

The Feather-Fin Pearl Fish (Cynolebias constanciae, now classified as Simpsonichthys constanciae) is a rare, beautifully patterned Brazilian seasonal killifish endemic to temporary freshwater habitats in the São João basin, Rio de Janeiro, Brazil. Reaching 5cm in length, this peaceful species is prized for its delicate appearance and fascinating breeding biology. As an annual killifish adapted to seasonal pools that dry completely, it has a compressed life cycle and unique reproductive strategy. Available for sale UK from Tropical Fish Co, this rare species rewards experienced aquarists with spectacular patterning and captivating behaviour.

Appearance and Coloration

The Feather-Fin Pearl Fish displays exquisite colouration with a slender, elegant body adorned in intricate patterns of blue, green, red, and yellow with pearl-like iridescent spots. Males are intensely coloured with elongated, feather-like finnage—particularly the dorsal and anal fins—that create a delicate, flowing silhouette. The fins feature intricate patterning and iridescent highlights that shimmer under subdued lighting. Females are smaller, plumper, and more subdued in colour with shorter finnage. In a planted tank with dark substrate, the colours and patterns become even more vibrant and eye-catching.

Natural Habitat

Cynolebias constanciae is endemic to temporary freshwater habitats (ponds) in the São João basin in Rio de Janeiro, Brazil. These seasonal pools fill with water during the wet season and dry completely during the dry season. The water is typically soft, slightly acidic, and tannin-stained, with abundant vegetation and a substrate of mud and organic debris. During the wet season, adults spawn rapidly; as pools dry, adults perish while eggs remain dormant in dried substrate, hatching when rains return months later.

Aquarium Setup

A minimum 20-litre aquarium is sufficient for a pair or small group of Feather-Fin Pearl Fish. Use a fine sand or soft peat substrate to replicate the natural spawning medium. Include live plants such as Cryptocoryne, Java moss, and floating species like Salvinia or Limnobium. Provide spawning mops or peat moss for egg deposition. Lighting should be subdued, and filtration gentle to avoid strong currents. A secure, tight-fitting lid is essential, as these fish may jump. Maintain excellent water quality and cooler temperatures (20-24°C) to replicate natural conditions.

Feeding and Diet

As a carnivore, Cynolebias constanciae requires a varied, protein-rich diet to maintain health and colour. Offer a varied diet of small live and frozen foods such as bloodworms, daphnia, brine shrimp, mosquito larvae, and quality small carnivore pellets or prepared killifish foods. Live and frozen foods are essential for conditioning and breeding. Feed small portions twice daily, removing uneaten food promptly to maintain pristine water quality. Variety and freshness are critical for optimal health and vibrant colouration.

Behaviour and Temperament

The Feather-Fin Pearl Fish is a peaceful species that spends most of its time exploring the lower and middle water column. Males may display to each other during courtship with flared fins and vibrant colour displays, but serious aggression is rare. These fish have a naturally short lifespan of typically 6-12 months, reflecting their annual biology. They appreciate a dimly lit aquarium with plenty of cover. They are not competitive feeders, so avoid housing them with boisterous or fast-moving species.

Suitable Tank Mates

Cynolebias constanciae is best kept species-only or with very carefully chosen peaceful tank mates of similar seasonal water requirements. Other non-aggressive killifish may be suitable only if size and temperament are appropriate. Small invertebrates are usually not suitable because they may be eaten. Avoid large fish, aggressive fish, fin-nipping species, very active boisterous species, and fish small enough to be eaten. A calm, quiet environment is essential for this delicate annual killifish to thrive.

Breeding

This is a seasonal killifish that typically breeds by laying eggs in soft substrate or peat. Condition a pair or small group with high-quality live foods, then provide spawning media such as peat moss or fine sand. Eggs are buried in the substrate and often require a drying/incubation period of several weeks to months before hatching. Collect eggs carefully and store in slightly damp peat in a sealed container. Fry hatch when the peat is re-flooded and require infusoria or newly hatched brine shrimp. Breeding success depends on providing the correct seasonal cycle and careful egg management.

Why Buy from Tropical Fish Co

Tropical Fish Co is a trusted UK supplier of rare and specialist tropical fish, including hard-to-find annual killifish species like Cynolebias constanciae. We guarantee healthy, well-conditioned stock, expert care advice, and secure nationwide delivery. Every fish is quarantined and inspected before dispatch, ensuring you receive only the finest specimens. Whether you're setting up a dedicated killifish tank or adding a rare species to your collection, Tropical Fish Co offers unmatched quality and customer service. Order online today and experience the beauty of Brazilian seasonal killifish.