GloFish Black Skirt Tetra Breeding Guide
Breeding the GloFish Black Skirt Tetra (Gymnocorymbus ternetzi): spawning biology of the black skirt tetra, with notes on its trademarked transgenic traits.
Overview
The GloFish Black Skirt Tetra is a genetically modified Black Skirt Tetra, Gymnocorymbus ternetzi, that carries a fluorescent-protein gene; its spawning biology is that of the wild black skirt tetra, an egg-scattering characid that gives no parental care. The fluorescent colour is a heritable transgenic trait, and GloFish is a registered trademark; in many jurisdictions the propagation and sale of these trademarked transgenic fish is restricted, so hobby breeding may be subject to legal limits.
Sexing
In the black skirt tetra, males are noticeably slimmer and a little smaller than females, and the male also has more pointed dorsal and anal fins than the female.
Conditioning
Condition the sexes separately on plenty of live and frozen foods at around 24-26 C (75-78 F) before attempting to breed.
Breeding Setup
- Spawning tank around 18 x 12 x 12 inches (about 45 x 30 x 30 cm), dimly lit.
- Temperature raised to about 28-30 C (82-86 F), several degrees above the main tank.
- pH on the acidic side of neutral.
- Clumps of fine-leaved plants such as java moss or spawning mops, or a mesh base that lets eggs fall out of reach of the adults.
Spawning Behavior & Trigger
Spawning can occur in a group of about six males and six females or as a pair. In pair spawning the fish typically spawn the morning after being transferred. Eggs are scattered among the plants or fall through the mesh, and the adults will eat the eggs, so they should be removed immediately on detection.
Egg & Fry Care
Eggs hatch in around 18-36 hours and the fry are free-swimming a few days later. Eggs and fry are light sensitive in the early stages and need dim lighting. First food is an infusoria-type food, progressing to microworm and brine shrimp nauplii.
Common Challenges
Besides the usual egg predation and light sensitivity, the trademarked transgenic status is the key consideration: fluorescence is inherited, but propagating GloFish may be legally restricted, and offspring colour and any selectively bred finnage are heritable rather than fixed.