This tube-shaped fin acts like a penis does in mammals. The female also has a black patch near her vent where fry develop. She will greatly increase in size as the fry develop. Breeding If you put at least one mature male and one mature female together in at least five gallons of water, and the temperature is between 65 and 80 degrees F, you will most likely be expecting fry soon. A female can retain sperm from a single mating to create several batches of fry.
Some books suggest placing more males than females together, unlike with other livebearers.
After about 24 days, the females will give live birth to 10-100 babies. In small tanks, the female should be placed in a net or birth box for livebearers when it looks like she is ready to pop. The fry should be visible as a black spot near her vent. After the babies are born, remove the mother from the box. She will eat her young as will most fish that see them.