Selective breeding is where art meets science. Start with high-quality, healthy pairs showing traits you want to pass on (color, fin type, size, etc).

Keep a breeding log. Track pairings, hatch rate, growth rate, aggression, deformities.

Cull humanely as needed to maintain quality lines.

Separate males early to avoid fin damage.

Use jars, cups, or partitioned grow-outs for sorting and monitoring.

Always outcross after 2–3 generations to avoid inbreeding.

Prioritize health and personality as much as appearance.