Cognate Killifish

Aphyosemion cognatum is a vividly coloured non-annual killifish from the Congo basin, where it inhabits shaded forest streams and pools. Males display a brilliant turquoise-blue body covered with dense red spotting that intensifies toward the fin margins, creating a jewel-like effect that makes this one of the more coveted Aphyosemion species. Females have an attractive greenish-brown colouration with faint spotting.

This species prefers very soft, acidic water with low dissolved minerals, reflecting the naturally tannin-stained blackwater streams it inhabits. A 40 L aquarium with peat filtration, fine-leaved plants, and a spawning mop is ideal. Eggs are collected from the mop and incubated in damp peat for two to three weeks.

A. cognatum is an intermediate-level killifish that rewards keepers who invest time in matching its water chemistry requirements. Its extraordinary colouration and the relative rarity of the species in the mainstream hobby make it highly desirable for killifish specialists.

Water: 22–26 °C, pH 5.5–7.0, very soft acidic water (GH 1–6) essential. Tank: 40 L species tank with peat filtration, floating plants, and a spawning mop. Feeding: Live Artemia, Daphnia, micro worms, and frozen bloodworm; feed daily. Breeding: Collect mop eggs every 7–10 days; incubate in damp peat for 2–3 weeks. Compatibility: Species tank or very peaceful nano community; very sensitive to water quality.