Knife Livebearer (Alfaro cultratus) — > 6cm

Overview

The Knife Livebearer (Alfaro cultratus) is a sleek, peaceful Central American livebearer celebrated for its streamlined body and elegant movement. Native to freshwater streams and rivers in Costa Rica and Panama, this active species thrives in planted community aquariums with gentle filtration. Available for sale UK-wide, the Knife Livebearer is an excellent choice for aquarists seeking a unique, easy-to-breed livebearer with moderate care requirements and engaging behavior.

Appearance and Coloration

Alfaro cultratus displays a slender, elongated body with a distinctive knife-like ventral profile, giving the species its common name. The body is typically silvery to pale yellow with subtle iridescence and a dark lateral stripe. Males are more slender and may exhibit extended finnage, while females are fuller-bodied, particularly when gravid. The large, expressive eyes and translucent fins create an elegant, streamlined profile.

Natural Habitat

The Knife Livebearer inhabits freshwater streams and rivers across Costa Rica and Panama. These habitats feature moderate current, abundant vegetation, submerged roots and wood, and clear to slightly tannin-stained water. The fish form small groups, foraging for insects, larvae, and small crustaceans at the water's surface and among plants.

Aquarium Setup

A minimum 75-litre aquarium is recommended for a small group of Knife Livebearers. Provide dense planting using species like Vallisneria, Amazon Sword, Java Fern, or Cryptocoryne, combined with driftwood and smooth rocks. Open swimming areas are essential, as this species is active and enjoys mid-water cruising. Gentle filtration maintains water quality without creating excessive current, and a secure lid is essential.

Water Parameters

Maintain neutral to slightly alkaline water with pH 6.5-8.0 and temperatures between 22-28°C. General hardness (GH) of 8-15 dGH is ideal. The Knife Livebearer is adaptable but performs best in stable, well-oxygenated water with excellent quality. Perform weekly water changes of 20-25% to control nitrate and maintain stable parameters. Avoid poor water quality or unstable chemistry.

Feeding and Diet

Alfaro cultratus is an omnivore that thrives on a varied diet. Offer high-quality flake or micro-pellets as a staple, supplemented with frozen and live foods such as daphnia, brine shrimp, mosquito larvae, and small insect prey. Include some vegetable matter or spirulina-based foods for balanced nutrition. Feed small portions 1-2 times daily, ensuring food is consumed promptly.

Behaviour and Personality

The Knife Livebearer is a peaceful, active fish that thrives in groups. This species is constantly on the move, foraging among plants and exploring the mid to upper water column. Males may engage in mild courtship displays, but aggression is minimal and rarely results in injury. The fish are generally non-aggressive and coexist well with other peaceful community species.

Tank Mates

Ideal tank mates include small peaceful community fish such as other non-aggressive livebearers, tetras, rasboras, and Corydoras catfish. Avoid large aggressive fish, fin-nippers, highly predatory fish, very boisterous species, and large cichlids. The Knife Livebearer coexists well with similarly sized, peaceful community fish in planted aquariums.

Breeding

Alfaro cultratus is a livebearer that breeds readily in captivity under good conditions. Provide stable warm water, dense planting, and a balanced diet to encourage breeding. Females give birth to free-swimming young after a gestation period of approximately 4-6 weeks. Fry should be separated from adults or provided with dense planting for shelter, as adults may predate young. Feed fry infusoria or liquid fry food initially, graduating to baby brine shrimp and crushed flake as they grow.

Why Buy from Tropical Fish Co

Tropical Fish Co is your trusted source for healthy, vibrant livebearers sourced from reputable breeders and quarantined for your peace of mind. We provide expert guidance on tank setup, water chemistry, and compatible stocking to help you create a thriving community aquarium. With fast, reliable delivery across the UK and a commitment to sustainable fishkeeping, Tropical Fish Co is your premier destination for unique and engaging freshwater fish.