Variable Pearfish, Blue-Ban (Cynolebias viarius) — > 4cm

Overview

The Variable Pearfish or Blue-Ban Pearfish (Cynolebias viarius) is a striking seasonal killifish native to seasonal freshwater pools and wetlands of Uruguay and adjacent southern Brazil/Argentina region. Reaching 4.5cm in length, this peaceful species is prized for its compact size, cool-water preference, and fascinating annual breeding cycle. As an annual killifish adapted to temporary habitats that dry seasonally, Cynolebias viarius has a compressed life cycle and unique reproductive biology. Available for sale UK from Tropical Fish Co, this rare species rewards experienced keepers with captivating displays and stunning colouration.

Appearance and Coloration

The Variable Pearfish displays variable but striking colouration with a compact, robust body adorned in intricate patterns of blue, green, and yellow with pearl-like iridescent spots scattered across the scales. Males are intensely coloured with elongated finnage and a bold presence, especially during courtship. The body features distinctive banding or barring patterns (hence "Blue-Ban") that create a dramatic effect. 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 viarius inhabits seasonal freshwater pools and wetlands of Uruguay and adjacent southern Brazil/Argentina region. These temporary water bodies fill with water during the wet season and dry completely during the dry season. The water is typically soft, slightly acidic to neutral, and well-vegetated, with 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 25-litre aquarium is sufficient for a pair or small group of Variable Pearfish. 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. Maintain excellent water quality and cooler temperatures (18-23°C) to replicate natural conditions and extend lifespan.

Feeding and Diet

As a carnivore, Cynolebias viarius requires a varied, protein-rich diet to maintain health and colour. Offer primarily live and frozen meaty foods such as bloodworms, blackworms, daphnia, brine shrimp, and small insect larvae daily. High-quality carnivore pellets or frozen foods may be accepted once acclimated. 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 Variable Pearfish 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 and are sensitive to stress, warm temperatures, and competition at feeding time.

Suitable Tank Mates

A species-only setup is recommended for Cynolebias viarius to accommodate its unique breeding biology, cool-water preference, and short lifespan. Avoid large fish, fast or boisterous fish, fin-nippers, aggressive cichlids, and competitive feeders. A calm, quiet environment is essential for this delicate annual killifish to thrive and complete its natural breeding cycle.

Breeding

This annual killifish typically breeds by laying eggs in a peat or fine spawning medium. Condition a pair or small group with high-quality live foods, then provide spawning media such as peat moss or fine sand. Eggs often require a drying/incubation period before hatching. Collect eggs carefully and store in slightly damp peat in a sealed container at cool room temperature. Fry hatch when the peat is re-flooded and require infusoria or newly hatched brine shrimp. Successful breeding depends on careful egg management and cooler water temperatures.

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 viarius. 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 South American annual killifish.