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It is normal for every living thing to reproduce. This is an important survival means for every species to ensure they do not become extinct. Both the fresh water and saltwater fish are not an exception. Just like any other species, the fish need a male and female to reproduce, but some of the fish species are capable of reproducing alone which means they are asexual.

In order to understand how the fish mate and reproduce, it is important to understand the reproductive organs. For any reproduction to occur and create a new life there must be a combination of sperm and egg. Despite the fact that there are different means by which this can occur, one common factor is the reproductive organs involved, which are the ovaries and testes. The vast majority of fish species are dioecious, which implies that the sexes are separated, with the males having testes while the females have ovaries.

Some of the species also have secondary parts popularly referred to as genital papilla. The genital papilla is a tiny tube that is located at the anus back in which the sperms are released. In this guide, we are going to look at the reproductive anatomy of fish and the various ways in which they mate. Thereafter, we will look at the most popular breed and look at how to create a perfect condition to allow you to breed them in the aquarium. Please enjoy.


There are three main reproductive strategies that can be used to classify fish. They include:

  • Oviparity
  • Ovoviviparity
  • Viviparity

Others include:

  • Parthenogenesis
  • Hermaphrodite


Just like in insects and birds, in the Oviparous fish, the embryo develops inside an egg but outside the parent’s body. Most of the bony fish belong here. This method requires the male to fertilize the eggs after the male has laid eggs. Most of the females can lay a lot of eggs once since laying eggs takes less energy than growing an embryo in an egg inside her body. The number of eggs that a female can be able to lay during a breeding season is closely related to the length and weight of the fish.

For instance, the Mola releases approximately 300 million eggs in one spawning season, while the silver Arowanas lay only 5 to 250 eggs per season. The fertilization process means it can either be by the male fish rubbing its sexes can happen in many different ways. It can either be by the male rubbing its sexual organs on the female, releasing sperms, or releasing the eggs in water for them to join the eggs in the zooplankton layer.

Below are some of the categories in which the egg layers fall.

Mouth brooders – In these species, the eggs are laid in water and then collected in the moth once they have been fertilized. Some of the fish species in this category include; Blennies, Betta, Cardinalfish, gobies, among others.

Egg Scatterers – In this category, the eggs are laid in an area that is usually under a cover, with no sticky eggs being laid in open water. Thereafter, the male swims through as it sprays the semen and it fertilizes the scattered eggs. Some of the species that belong to this category include; Tiger bards, Cardinal tetras, Goldfish, among others.

Nest Builders – The male and female usually build a nest that is made from plant materials or a bubble nest, and then they deposit the eggs there for the male to fertilize them. Some of the species in this category include; Bluegills, Bettas, Gouramis, among others.

Egg Depositors – In this category, the eggs are laid by the female at one point, and then the male swims past them and fertilizes them. Some of the common fish n this group include; Dwarf cichlids, Clownfish, Killifish, among others.

Egg Buriers – In this category, the eggs are usually put inside at the substrate, and then the male gets to fertilize the eggs.


These two species are what are commonly referred to as live-bearing species. This implies that they give birth to live fry. Mostly, these species are usually small in size and vulnerable and are in most cases eaten by their own mothers. One of the examples of livebearers includes guppy fish. The gestation period of a common aquarium fish will take approximately 25 days. In this category, the males are relentless, and the reproduction usually continues throughout the year. After giving birth, the female is usually ready for another conception.

In this, the male and female will mate, and the fertilization will take place inside the body of the female, and then she will give birth to a large group of fries. Here the male possesses agnopodium fin, which is a modified tubular anal fin in which the sperms are released from and then into the female for fertilization to take place. In the Viviparous, the fry usually develops inside the body of the mother while taking the nutrients directly from the mother and not the York, while in Ovoviviparous, the egg that is inside the body of the mother provides all the necessary nutrition. They are released when they are grown up.


In these species, the females create a genetic clown of themselves. The offspring are, therefore, females too. These fish are unique and rare. The reproduction needs two ingredients a single egg cell and a single sperm cell. Each of the cells provides half of the genetic information needed to create new life. However, in this category, the cells find a crazy method of filling in for missing genes. The missing genes are normally provided for by the sperm cell.


This is another interesting phenomenon within the fish, and In this one, the fish possess both male and female reproductive organs. They will come into two forms a fish that can change from a male to female or a fish that can be a male and female at the same time. The fish that is both male and female at the same time does not need a mate. One of the fish that belong to this group is the Killifish. It produces eggs and sperms at the same time. This process is known as synchronous hermaphroditism.

The most popular fish that belongs to the hermaphrodite is the clownfish. The male is capable of turning into a female within a group; this process of male turning to female is known as a protandrous hermaphrodite, while the process of female to a male is called protogynous hermaphrodite.


The reproductive organs are the slowest in terms of growth since they are not important for survival during birth. Different fish species have different ages at which they achieve their sexual maturity. The readiness is determined by the species, age, and size of the species. In general, what it implies is that the smaller the size of the adult fish, the sooner they will attain the reproductive age. Some start to reproduce a short while after being born, while others take care to reproduce.


The cycle of reproduction greatly varies depending on the species. Some of the fish reproduce many times in a year, such as the mollies, guppies, clownfish, among others, while others reproduce at a specific time of the season while others reproduce once and die when their eggs and sperms are released.



As you choose your fish, you need to ensure that you have at least one male and one female, but the ratio depends on the species. Most of the fish are either sexually isomorphic or sexually dimorphic.

Sexually dimorphic– These species can easily be identified by just staring at them. Their reproductive organs are shaped differently, and the size, shape, and color are different. The males are usually large and more vibrant compared to the females.

Sexually isomorphic – These species have very few differences if any, and this makes it a bit difficult to differentiate them. Sometimes it becomes so hard to distinguish them, and the only way to do that is by looking at the genital papilla during the spawning period.

Apart from selecting the right sex, you also need to ensure that the parent fish have great coloring and patterns and also ensure they are healthy and mature. It is also good and important to ensure they are compatible since, in some species, pairing can only happen within a group that has been raised together. This happens in some cichlids species. If a new species is just thrown in them, they may get bullied to death.

If you are choosing a species that is difficult to breed, you should keep a close eye on those that are showing some courting behavior. Once you have found and chosen the suitable pair to breed, they should be conditioned. Conditioning implies that you should feed them with the right food to ensure they are in their best condition to breed. If you get your fish during the late winter or early spring, they are likely to be conditioned already, and they will be ready to breed.


It is important to understand the tank conditions, size, breeding environment, and spawning behavior of every species before you can breed them. Some of the species need a bare tank or a separate tank for breeding and raising the fry, while others require certain plants and water flow.

Ensure that you bring the ph and the water hardness to the desired levels and also raise the water temperature by about ten degrees F from its normal temperature. Also, separating the male and female using a glass partition where they can see each other increases the desire to breed when they are given a chance.


It is important to separate the parents from the fry irrespective of the behavior pattern of that individual species. This is because it will give the young ones the space to live out their lives and compete evenly without any intimidation. Also, they will be saved from the danger of possibly being eaten by the larger fish. However, you should not forget to return the temperature to the normal range once the spawning period is over. The fry should then be provided with the right diet that will support their development.


In this section, we are going to take a closer look at how popular fish species breed. They include the Goldfish and bettas. We are not going to look at some of the breeds, such as the guppies, since they are quite straightforward to breed, and they do not need strict tank conditions.



Before attempting anything to do with mating, it is crucial to have the right tank conditions. You will also need a sponge filter, floating plants, newly hatched brine shrimp, or any other food that the hatched fry can feed on. Every tank that you are putting fish into should be cycled. The water in the aquarium should be heated above the normal temperature to about 82 degrees F. Before attempting to breed, ensure the rest of the water parameters such as ph and hardness are within the recommended range. If you are using a separate breeding tank, it should be between 5 to 10 gallons. Before intruding the male and female to each other, place a removable and transparent divider in the center to separate the male and female before you introduce them together.


The male Bettas reach sexual maturity at the age of three and half months. You realize that they are ready to mate when you see them establishing some bubble nests. The female, on the other hand, develops an upright bar marking on the side of their bodies which indicates that they have reached sexual maturity too. Once the males have built the bubble nest, you can now remove the divider. When they are placed together for the first time, you may find them fighting. This should not worry you since it is normal, but you need to keep an eye on them to ensure none of them is injured.

If the male has some interest In the females, he will flare out the gills, spread his fins, and twist his body. If a female is interested, she will curve her body back and forth and turn a darker color. When the female is ready to pair, they will spend most of their time near the bubble nest. The male will then circle her and take some time to determine the best positioning. They will then proceed to embrace each other for a few seconds, and then the female will release the eggs. Each time they embrace each other, the female will release 10 to 40 eggs, and this will go on until the female has no more eggs to release.

As soon as the female has finished releasing the eggs, she should be removed from the tank. Once she has been moved, the male will then fertilize these eggs by releasing milt into the tank. The male will then collect these eggs from water and put them into the nest, and continue to take care of them for the next 24 to 36 hours. He will remain there and will be returning the eggs in the nest in case they fall. The male remains in the tank until the fry emerges.



Before engaging in breeding this fish, you need to ensure that the tank is large enough to accommodate the adult clownfish and it is fully cycled. The tank should be well planted and kept at around 64 degrees F for about four months. The tank should then be warmed again slowly to the range of 70 to 74 degrees F for a two weeks period. This will mimic their breeding season, which they are used to in the wild, and will initiate breeding.


At this stage, you should ensure that you have at least three-year-old male and female in your aquarium. The younger fish can also reproduce, but they can become egg bound which is dangerous to them. Some of the visible signs that your fish is ready to mate include the white spots along the gills of the males, and the females will become fatter and more rounded.

The male will then start chasing the female around the tank in an attempt to lure the female to release the eggs. This stage needs a lot of energy and when the female becomes too tired, and she cannot continue, she will go ahead and release the eggs. The average number of eggs she will release is 10 000.   The eggs then stick on the plants and the walls of the tank, and then the males will release the milt and fertilize them. This may at times make the water cloudy, but it is normal. The eggs that are fertilized will appear clear, while the unfertilized ones will be white. Ensure that you remove all the unfertilized since they will develop some fungus which will lead to water pollution. You can now move the eggs to a different tank to avoid being eaten by the adult fish.


The fish are different from human beings since they do not have parental instincts. This explains why after the eggs have been laid, it is crucial to watch them closely, and you have to make a separate aquarium for them finally. If the young ones and the parents are put together, the parents will eat the young ones.

Also, different types of fish have different ways of mating and reproducing. Some keep it plain and simple, while others it is a complex process. It is upon the owner to establish the mating method their fish usually take in order to take the appropriate measure.

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