How the method works

Fish that fertilise eggs internally and release free-swimming young rather than laying exposed eggs.

Practical breeding setup

Use stable water, dense cover or a separate nursery plan, and a realistic population-control strategy. Pregnancy boxes are not a substitute for space, observation and water quality.

Egg and fry management

The young are comparatively large and can usually take fine prepared foods or newly hatched live foods soon after birth.

Main failure point

The main failure is not getting fry—it is uncontrolled population growth, inbreeding, overcrowding and exhausted females.

Fish in this category

The database currently contains 8 commonly kept fish assigned to this main method. Some fish also show secondary behaviours, and individual parental care can vary.

Common mollyPoecilia sphenops6–10 cmOpen entry →Endler’s livebearerPoecilia wingei2–4 cmOpen entry →GuppyPoecilia reticulata3–6 cmOpen entry →Least killifishHeterandria formosa2–3.5 cmOpen entry →PlatyXiphophorus maculatus4–7 cmOpen entry →Sailfin mollyPoecilia latipinna10–15 cmOpen entry →SwordtailXiphophorus hellerii8–14 cm including swordOpen entry →Wrestling halfbeakDermogenys pusilla5–7 cmOpen entry →

Originality and limits

This guide explains the shared breeding pattern in original AquaNexus wording. It is not a substitute for the individual species entry, because temperature, social structure, egg size and parental behaviour differ.