Fish Care

How do fish mate and how to breed fish in your fish tank

how do fish mate

If you are into fish keeping, one common question you may likely get is how do fish mate. In this article, we will take a look at the reproductive life of a fish, the different ways in which fish breed.

We will then discuss how you can create the right conditions to properly breed them in your aquarium.

All living things reproduce; this is an important part of the life of each specie to ensure they don’t go extinct. Freshwater and saltwater fish are no exception. Apart from their different varieties, all fish share two common characteristics. First, they are vertebrates, which means they have a backbone. Any aquatic organism that does not have a backbone does not belong to the fish family. Another factor is that they only live-in water and cannot survive on land.

Other than that, some of their features are very different, including different ways of mating and starting a new life.

How do fish mate?

In order for fish to reproduce, sperm and egg must be combined to create a new life.

While there are a few different ways this can happen, one common thing is the reproductive organs involved; eggs and testicles. Most male fish have two equal testes – which may be partially or completely combined – while female fish have eggs. There are a few species that contain both sets of organs (hermaphrodites); we will discuss this later in the article.

Some species have a second organ known as genital papilla. This is a small fleshy tube found on the back of the anus from which semen is extracted.

Genital papillas, which play a key role in the release of sex cells (either sperm or egg cells as possible) are another important reproductive factor in fish. The papilla of the genitals is the fleshy tube located behind the anus, and its shape is often used to distinguish between male and female fish. The papilla of the male sex organs is usually enlarged and pointed while it is feminine, broad and round.

Now to answer the question of how do fish mate;

  1. Egg laying

This involves the process by which a female fish lays eggs and is fertilized by sperm from a male fish. Most females can lay large number of eggs at a time, because they take much less energy than they do to develop an embryo in their body. The fertilization can be done in a various way; it could be a male fish who rubs his reproductive organs on the eggs then releasing sperm directly on the eggs, or removes sperm into the water to join the eggs in a layer of zooplankton (if the eggs are laid that way).

Egg laying fall into one of these categories:

  • Mouth brooders

how do fish mate

“Mouthful of babies – Ostorhinchus limenus #marineexplorer” by Marine Explorer is licensed under CC BY-NC-SA 2.0

In the mouthbrooders category, the female lays her eggs and the male fertilizes them. Then one of the fish collects all the eggs and holds them in its mouth until they hatch. Examples of mouthbrooders are (Bettas, Cardinal fish, Blennies, Gobbies & freshwater Cichlids).

While the length of time varies depending on the species of fish, some might mouth brood for weeks at a time. In most cases the male is responsible for carrying the eggs and during this time he eats less or does not eat.

The benefits of Mouthbrooding include complete protection of the eggs up to hatching and high levels of oxygenation with constant flow of water. The eggs are kept easily clean and turned into a process again.

In some species, their fries are totally on their own once they are hatched. While some are given care until they look like small adults, at this stage they can swim very well and can escape predators on their own successfully.

Do fish sleep? Find out all you need to know about betta fish sleeping patterns

  • Nest builders

It is made from plant materials or a bubble nest, which is usually built by a male and a female and then lays its eggs there and the male builds them. These foam nests are blown up in areas where there is a lot of oxygen and a source of food, increasing the survival rate of the offspring. After hatching, both parents care for the children. (Bettas, Gouramis, Bluegills & Stickle-backs).

  • Egg- scatterers

In this category, the female fish scatters her eggs while the male follows closely to fertilize each egg. The female fish lay sticky scattered in places but often in areas that provide some sort of cover, while others lay eggs that are free to move in open water. (Tiger Bards, & Goldfish).

  • Egg Depositors

Egg depositors, lay their eggs on one particular spot usually at the bottom substrate and sometimes on an aquarium glass. Then the male swims down to the bottom of the substrate to fertilize them. (Killifish, Dwarf Cichlids, Clownfish & Rainbowfish).

  • Egg Buriers

Egg buriers go into the soft substrate or the male pushes the female into the soft substrate to lay. The male dives to fertilize the eggs. In the area of ​​breeding tanks, peat moss is usually a good choice of substrate (Killifish).

  1. Livebearers

In livebearers, the female is impregnated by the male anal fin which is known as gonopodium. Sperm is being released from the fin into the females body in which she undergoes fertilization and the development of the embryo which takes place inside of her.

Within a month, the female will release a hatched fish, also called a fry or larval fish.

These young fry’s are fully formed and ready to swim from the time they hatch. Soon, they started looking for food as they needed to survive. In this sense, it is the strongest survival since the fish hatched and plunged into the water.

As for the mother fish, she can continue to release a larvae fish once a month for the rest of her life, without the presence of a male! Therefore, in this type of mating, the presence of male sperm is required only once and after that, the female is independent enough to continue breeding alone.

Most survivors have fewer fries and are larger than egg layers because the fry needs to be more developed and large enough to be independent after birth.

  1. Unisexual

Some species of fish breed on their own without the help of a mate. All these fish are female and give birth only to females. There is no need for a male presence. Although we cannot call it mating, because it shows that the role of sperm is not entirely in the reproductive process.

Occasionally, females may come in contact with male fish of different species (closely related), but sperms are not used for reproduction.

  1. Hermaphrodites

Hermaphrodites have both male and female reproductive organs.

There are two types of hermaphrodites. In the first stage, male and female, mate and lay eggs. For example, a fish can be born a male and a few years later, a female. This is called congenital hermaphroditism.

When a male change to a female, the process is called protandry and when a female changes into a male, it is called a protogyny. However, both breeders still need fish of the opposite sex to breed

Clown fish is an example of this form of hermaphroditism. Each clown fish group will consist of two large fish, one male and one female. All other small fish are all male. These fishes live among the sea anemones. When a female fish leaves a group, its mate switches to the female and the next largest fish increases in size to become the new female’s partner.

In another specie called the Indo-Pacific cleaner wrasse, there is only one male fish while the rest are female. When a male fish leaves or is killed, the female becomes a male and the next big fish grows into a mating mate.

This kind of hermaphroditism is called simultaneous hermaphroditism. In some examples of simultaneous hermaphroditism, one fish may function as a male and a female. Slugs, for example, fall under this category. Sometimes, a creature may show its male or female organ and another slug shows the opposite. Therefore, the two mate and produce offspring. This is similar to the general mating process in other creatures, except that the fish can be male or female.

  1. Substrate Spawners

This is a very complex process on how fish do mate, the female releases her eggs and the male fish releases his sperm into the water. Both fish release eggs and their sperm in close vicinity, but the fertilization occurs by chance. Not all eggs are fertilized by sperm.

Frys (young fish) from this breed are able to strong and adapt well to survive from the first seconds. This is because none of the parents are there to protect the fish from harm.

This type of breeding is also called synchronous or mass spawning. Examples of fish that mate in this way are jellyfish, sea anemones, clams and fan worms.

When is the fish old enough to reproduce?

The reproductive organs are usually slow-growing organs because they are not essential for survival at birth.

Different species reach sexual maturity at different ages; their suitability depends on the species, the size and age of the fish.

Some fish start to reproduce very quickly after birth and some take years to reach maturity before they can reproduce.

 How often do fish mate and reproduce?

The breeding cycle varies greatly depending on the species.

Some fish breed several times a year (eg Clownfish, Guppies, Mollies, Swordtails and Platys), some breed only once in a while, and some breed once and die when sperm or egg is released (e.g. Pacific Salmon).

Livebearers vs egg layers

If you are just getting started, we recommend that you start with breeding livebearers. Generally, they are easier to reproduce than egg layers.

Species like Guppies and Platies do not require much help or special conditions and are therefore a good choice for first breeders.

Once you have some experience breeding livebearers, you can move on to egg-laying fish such as Barbs and Danios.

The benefits of breeding livebearers rather than egg layers are that the parents easily mate without much help and they are much less needy once their frys are born. And the fish can lay hundreds of thousands at a time. They prefer quantity over quality and it works well enough.

However, small fries are also weak and are mostly eaten before they are fully grown. Also, livebearers tend to have a well-developed young frys compared to other fish.

How to breed Fish in Your Aquarium

Breeding fish in a home aquarium requires careful monitoring and preparation. It is not as easy as simply sticking a male and female species together and hoping for the best.

  1. Choosing the Right Parent Fish

The biological differences between species can vary greatly, but there are a few common features that you should look for. Female cichlids, for example, tend to have more rounded bodies and less pronounced vents, while males tend to show brighter colors and sometimes have a slight hump on their head.

  • It is advisable to only breed fish of the same species. While it is possible for two different species to produce, there is a good chance that the emerging hybrid will be weak, deformed or sterile.
  • Do not breed with fish that appear sick, deformed or injured. It is less likely to produce healthy offspring.
  1. Setting up a breeding tank

Since the fish is not in its natural habitat and now lives in the aquarium you have created for it, you will have to provide it with the right (natural) conditions. Therefore, when setting up a fish tank for  breeding, it is important to understand the tank conditions, size, breeding environment and reproductive behavior of each breed if you want to breed successfully. Some species require bare tanks or a separate tank for breeding and growing fry, some species require certain plants, water flow.

Bring the water pH and hardness to the required levels (for each specie) and also raise the tank temperature by about 10F above normal temperature.

By separating the male and female fish by the glass separation, this also increases the desire to mate when given the opportunity.

  1. Caring and protecting for the fry

Remove the parent fish from the old tank. Once the female has laid her eggs or gave birth live, remove the frys from the tank and put them in another. This will protect the eggs from being disturbed long enough for the fry (newborn fish) to hatch. Keep the tank conditions the same.

  • With the exception of a few types of feed, it is common for older fish to eat their eggs.
  • If it is not possible to set up a separate frying tank, add lots of plants and other body structures to give them a hiding place once they are capable for swimming.
  1. Reduce the amount of light entering the tank

Cover the tank on 3 sides with paper or pieces of fabric thick enough to block out too much light from the outside. Newly hatched eggs and fish are often sensitive to light – much of which can be frustrating or even kill them. As they continue to grow, their tolerance will increase and you can restore the aquarium to its original light levels.

  • Be sure to cover up the sides that get the most direct light. Leave one of the larger sides uncovered for viewing.
  • You can even leave the tank completely covered with a sheet when not feeding or watching them.
  1. Change the tank water daily

Practice draining the tank by 25-50% and adding fresh water at the same time each day. Clean water is needed for the fry to learn to breathe and filter on their own.

  • Draw from the same source each time you fill the tank. It is important that fresh water has the same basic composition as the old.
  1. Feed young fish several times a day

When the fry hatches for the first time, they come armed with a large yellow egg sac that provides sustenance for a few days. Once the egg sac has disappeared, you will need to start feeding yourself. Egg yolks, crushed fish juice, plankton and algae are examples of foods used for feeding fry.

  • Look for the food you need at pet stores. As always, do your homework to find out which foods are best for the species of frys you have chosen to breed.
  • Smaller species such as tetras and rainbowfish, for example, will not be able to handle food prepared for sale immediately after hatching, and need to be fed infusoria or similar supplement that can be easily digested.
  • As the fry gets older they can start feeding on substantial foods such as brine shrimp and microworms.

There are different ways fish breed and reproduce. Some species of fish are relatively easy to breed than others. So, if you are a beginner, start with one of the simpler and easier breeds listed above.

The conditions of tanks and mating process varies depending on the specific species, so if you are an experienced fish keeper who wants to breed the most complex species, always research the conditions they need.

Understanding all of these factors is important in fish breeding and for keeping them in an aquarium.


Leave a Comment