Spawning Methods

Spawning Methods

Sexually, fish can be classified into two groups: the sexually dimorphic and the sexually isomorphic species. The sexually dimorphic species show obvious primary and secondary characteristics of their gender. The males of this species are often larger and more colorful, and they usually have a much more elaborate finage. The sexually isomorphic species show hardly any apparent differences in the two sexes. It is therefore very difficult to distinguish between the two sexes in this group. Often, the only deciding factor could be the shape of the genital papilla. This becomes visible at the time of spawning. In some of these species, the female have a more rounded belly or is slightly larger than the males. There are some species that show no visible difference at all between the two sexes.

External fertilization followed by egg laying is the way most fish in aquariums will reproduce. Egg layers are classified into five groups:

Egg Scatterers

These species, as the name indicates, scatter their eggs on any surface. The eggs may be adhesive or non adhesive. After laying eggs, the parents do not look after them, and may even eat their own eggs. These are mostly schooling fish, and they often spawn in groups. Their eggs hatch fairly quickly.

Egg Depositors

These fish deposit their eggs somewhere on the substrate. They lay fewer eggs than egg scatterers. Some species within this group show advanced care for the eggs and fry. They will deposit eggs in an enclosure, cave, a pit or similar, and protect and clean the eggs. Some species of Cichlids come under this category. Not all egg depositing species care for their young. Some just deposit their eggs and then abandon them. Egg depositing species generally don’t eat their own eggs. Their eggs are usually larger than those of the scatterers.

Mouth Brooders

There are two basic types of mouth brooders. In some species, the female fish carries the eggs and/or larvae in its mouth. The female in this group receives a mouthful of sperm from the male, and the fertilization takes place in the mouth of the female. In the second type of mouthbreeders, the females lay the eggs on a substrate and guard these eggs till they hatch. Once the eggs hatch, she picks up the fry and carries them in her moth till the fry have become a little bigger. There are also paternal mouthbrooders where the offspring is carried by the male fish.

Nest Builders

These fish build a kind of nest that is made of plant debris and saliva. They may also dig a pit in the substrate to lay eggs. They take care of their young ones.


Livebearers are fish that do not lay eggs. The fry come already hatched out of the mother fish. Livebearers are able to give birth to young ones because of internal fertilization which takes place inside the female. Sometimes contact between the cloacal apertures of the male and female fish leads to fertilization. In some species, the eggs produced by the livebearer will be heavily yoked. In other species, the young are in direct contact with the mother and are fed and nourished by her. In this case, the mother carrying the young ones needs more nutrition and overall care.

Fry of livebearing fish usually takes about 30-32 days to develop. Many factors will affect this development period, e.g. the water temperature, the female's age and her level of nutrition. The good thing about livebearer females is that they are immediately ready to breed again after they drop their young ones. The competition to get to these females is intense among the males.

For beginners livebearers are the easiest fish to breed. If given enough space, the livebearers will do most of the hard work. Once the fry become noticeable and have started swimming, they need to be removed from the aquarium unless the aquarium is densely planted. Failure to do so will surely land a large percentage of them into the stomachs of bigger fish. Many people breed livebearers to provide food for predatory fish. Some livebearers will cross breed with other fish and to avoid hybridization these species should not be kept together.

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