Breeding Cardinal Tetra
How to breed Paracheirodon axelrodi: sexing, very soft acidic blackwater, dim light, fine-leaved spawning medium, and care of the light-sensitive eggs and fry.
Overview
The Cardinal Tetra (Paracheirodon axelrodi) is an egg-scattering characin whose captive breeding is rated advanced. It was historically difficult to breed in captivity, although many breeders now produce the species by mimicking its natural blackwater conditions.
Sexing
Females are noticeably rounder-bodied and slightly larger than males, an outline that becomes apparent when ripe eggs are present in the reproductive tract. Males have very flat, almost straight-line bellies.
Conditioning the Breeders
Condition the fish on plenty of small live foods. For group spawning use about half a dozen specimens of each sex; for pair spawning select the fattest female and best-coloured male.
Breeding Setup
- Light: very dimly lit; eggs and fry are light-sensitive in the early stages
- Water: pH 5.5-6.5, hardness around 1-5 (very soft, acidic)
- Temperature: 24-29 °C (about 80-84 °F)
- Spawning medium: fine-leaved plants such as java moss, spawning mops, or a mesh base eggs fall through
- Filtration: a small air-powered sponge filter bubbling gently
Spawning Behavior & Trigger
The male pursues the female into fine-leaved plants and the pair release eggs and sperm together. Spawning tends to occur during the night, often around midnight, and has been observed even with the aquarium lights on, the fish retaining their night-time colour pattern.
Egg & Fry Care
Eggs hatch in 24-36 hours and the fry become free-swimming 3-4 days later. Keep the tank dark because the eggs and fry are light-sensitive early in life. First foods are an infusoria-type food, progressing to microworm or brine shrimp nauplii as the fry grow.
Common Challenges
The species demands very soft, acidic water for fertilisation, and the light-sensitive eggs require darkness. Recreating the shaded, tannin-rich blackwater of its natural streams is the key to consistent success.