Freshwater

female is usually larger and more full-bodied than the male. Most males have
a rodlike organ (developed from the anal fin) called a gonopodium. This
unique organ is used to internally fertilize a female. After a single fertilization,
a female can produce multiple broods (batches of fry) month after month
without a male being present.
Except when they’re in drag
In some livebearers, females can develop secondary male sexual characteristics.
Where not enough males are present to ensure survival of the species,
the female’s anal fin may change into a gonopodium, and that fish will then
carry on male duties!
The egglayers
Chapter 20: Let’s Spawn!
Egglayers lay eggs (which usually range in size from 1.4 to 3 millimeters) that
eventually hatch into newborn fry. The fry of egglayers are not as hardy and
fully formed as those produced by livebearers. The babies of egglayers take
much more time to mature. Popular egglayers include angelfish, cichlids,
goldfish, and bettas.
When breeding egglayers, be aware of the following dangers to eggs:
Lack of oxygen: The eggs in your breeding tank can be seriously damaged
by lack of oxygen in the water. Without oxygen, their normal rate of
cell division decreases. But you don’t want heavy turbulence in the tank
either. Hook up a small airstone or bubble disk (which splits the air into
smaller bubbles) to a gang valve (which splits up an air supply to supply
several pieces of equipment) so that you can adjust the oxygen flow.
This setup provides beneficial aeration for the eggs without blowing the
eggs into the next county.
Poor water conditions: Dirty water can cause eggs to deteriorate. Make
sure your water is clean and has the proper temperature and pH for
your species.
Lack of vitamins: Eggs can also be damaged if the mother lacks the
essential vitamins needed to help them grow correctly. Diseased females
can produce bad eggs. If the eggs from an unhealthy mother hatch, the
young are usually defective and will produce deformed babies or none at
all. Make sure that your spawning female is in good health before you
attempt to breed her.
Intense lighting: Light that’s too bright can also damage fish eggs.
Minimize lighting in your breeding tank.
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