How Do Fish Mate: The Ultimate Guide For Fish Breeding


How Do Fish Breed?

Different fish have different ways of mating and producing offspring. While most species require male and females to produce offspring, some can produce babies without the need of a mate at all.

Breeding your fish in your aquarium can be the most rewarding accomplishment in the hobby. You will see a pair of fish, you selected, produce offspring that you can then raise to maturity.

It is extremely important, if you are thinking of breeding your fish, that you research their specific breeding practices. Different fish breed in different ways and you want to ensure that you are prepared.

Fish Reproduction Organs

Fish typically need sperm from male testes and eggs from female ovaries to produce an offspring. They may also have a secondary organ that can increase reproductive productivity, this is called the genital papilla.

The papilla plays an important is a fleshy tube that sits just behind the anus, it releases sex cells to increase the reproductive fitness of the fish.

The papilla can be used to determine the sex of a fish – male fish papilla is usually elongated and pointed while female papilla is oval shaped and broad.

Types of Reproduction

There are a number of ways that fish mate. Some will definitely shock you:

  1. Sexual Reproduction

Most commonly, fish reproduce by fusing sperm from testes with eggs produced from ovaries. This is because most fish have separate female and male sexes.

Some species of fish also have secondary organs called genital papilla.

  1. Hermaphrodites

Some fish are hermaphrodites and have both testes and ovaries, such as clownfish.

They often undergo sequential hermaphroditism where they are born one sex but change to the opposite sex after a couple of years.

Females turning into males is called ‘protogyny’ and males turning into females is called ‘protandry’.

Often the switch in sex is a result of the fish group being deprived of the opposite sex. If the group is lacking a female for example, one of the fish will switch sexes to be a female so that the group can breed.

Hermaphrodites can typically only produce either sperm or eggs at one time, so they must have another member of the species to cross-fertilize.

There are some hermaphrodite fish species that can produce both eggs and sperm, such as salmon and hamlets.

Asexual Reproduction

A rare type of breeding is found in parthenogenesis fish. These are fish that can reproduce entirely by themselves.

The female egg will develop straight into an offspring, without the need of fertilization from a sperm cell.  The offspring is a complete copy of its mother.

How Do Fish Mate?

There are two categories of fish when it comes to breeding – the live bearer and the egg layer.

Live Bearers

In this method of mating, the male transmits the sperm into the female with the use of his anal fin. The sperm fertilizes the female’s eggs insider her oviduct.

The female will then birth the live fry about 3 or 4 weeks later. The young will be fully formed and able to swim as soon as they are born.

Some examples of live bearing fish are swordtails, goodeids and guppies.

These types of fish are less difficult to breed typically and have a wider range of survivable water conditions.

The development of the embryo depends on whether these fish are viviparous live bearers or ovoviparous live bearers.


  • Vivaparous live bearers have a placenta-like-structure. This attaches the mother to the embryo and acts as a medium, providing the embryo with nourishment from the mother’s body.
  • Ovoviparous live bearers’ eggs are fertilized internally but they are nourished by the yolk sac inside the mother instead of receiving nutrition from the mother’s body.

Egg Layers


In this mating method, female fish lay eggs and those eggs are then externally fertilized by a male’s sperm.

How Do Fish lay Their Eggs?

Different fish species have different ways of laying their eggs:

Nest Builders


These fish build some sort of nest for their eggs, usually it is a bubble-nest created from plant debris and saliva coated bubbles.

Betta and Paradise Fish for example, build bubblenests where fertilized eggs are kept before they hatch. Bubblenesters have great parental instinct and the male tends to stay and protect the fertilized eggs in most cases.


Egg Scatterers

Eggs are littered their surrounding environment, either under cover or in an open water area. The eggs are fertilized by the male fish, who follows the female while she is laying her eggs.

Some examples of egg scatterers are Tetras, Danios, and Koi.

Egg scattering parents don’t offer any protection to their eggs and are more likely to eat them. If you are breeding with egg scatterers, you must separate the eggs before they hatch so that this doesn’t happen.



These types of fish collect their fertilized eggs in their mouths. It is the male that broods the eggs in his mouth until they hatch.

Often these types of fish will eat their eggs.

Some examples of mouthbrooders are Jawfish, Sea Catfish, and Cardinal fish

Egg Buriers


These fish usually live in water that dries up at some point in the year. The parents, who mature very quickly, want to lay their eggs before the water dries up and they die. So, they lay them in the ground.

The eggs remain dormant until it rains, which stimulates them to hatch.

Egg Depositors

This type of fish deposits their eggs in one place, usually some sort of a substrate. Some egg depositors care for their eggs and some don’t.

When to breed fish

Deciding when to breed fish depends on where the fish are native to and when they would naturally breed.

Most fish species are ready for breeding in the Spring. During the spring, the water is warmer and daylight is longer.

Doing water changes more regularly, increasing the temperature and leaving the lights on for longer will help to replicate this for your fish.

Prepping the Aquarium

Create an environment as similar to what they would have in nature.

Feed them a diet high in protein for about 3 to 5 days to make them healthy and robust, increasing the likelihood of a successful breed.

Different plants, decorations, tank setups and breeding surfaces can help to stimulate breeding for various fish species. That’s why it is important to thoroughly research your fish species so that you can make give them the best environment possible for breeding.


As always, it is extremely important to check the levels of nitrogen and ammonia in the tank. These compounds are harmful and maybe even deadly to your fish and especially to fry.


Selecting a Breeding Pair

Be sure to research your individual fish before breeding them. They all have different requirements and behaviors that you need to understand.

Be able to distinguish between males and females.

You want to be sure that both of the parent fish are healthy. Check all the physical and behavioral signs.

Make sure they are a good color and size and that they have overall vigor. If they are not energetic, of their colors have dulled, then they may not be in the best health.

You can find fish in your local aquarium that are conditioned and ready to breed in late winter or early spring.

Be sure to find out whether it is safe to leave the eggs or fry with the parents.

Many different types of fish will eat their offspring, so you may need to separate them.

After Breeding Your Fish

More often than not, it is best to separate the parents from the fry. This will give the fry space to grow without intimidation. This also eliminates the risk of them being eaten by either their parents or other fish.

If your fry are from an egg laying fish, don’t feed your them when they first hatch as they will still have a yolk sac to feed off for a few days. Once that has been fully absorbed, you can introduce food.

You should provide your fry with adequate foods and tank requirements so that they can grow and develop healthily.

Adding plants and decorations is a good idea so that your fry can have places to hide and play.

Again, it is important to thoroughly research the breed of fry you have bred so that you can ensure that you give them optimal conditions to thrive in.


The way that fish breed is fascinating. If you get to see it for yourself in a fish tank it is one of the most rewarding parts of being a fish owner. As long as you carefully research how to breed the specific fish you are using, you should have a wonderful experience.

We humans only know sexual breeding, so it is mind blowing to see all the different ways that fish are able to produce offspring, some even doing so without a mate all together. I hope you learned something from this article, and good luck if you are hoping to breed your own fish!

Frequently Asked Questions

What is the easiest fish to breed?

Livebearer fish are usually easier to breed. Some popular choices are Guppies, Platys, Swordtails and Killifish.

Can Fish Breed in a Community Tank?

Yes, they can but they can become territorial when breeding and guarding their offspring. It is a good idea to keep them in a tank with peaceful fish to avoid any aggression. It is also important, most of the time, to keep your fry and eggs in a separate tank. Their chances of survival in a community tank are definitely not as good as if they are on their own.

What Fish Don’t Eat Their Fry?

There are a few species who will protect their babies rather than eating them. Mollies don’t eat their fry. Dwarf corydoras also don’t typically eat their fry. Cichlids are known for being good parents – they will protect their eggs and fry too.

Do Goldfish Eat Their Fry?

Goldfish do eat their eggs and their fry once they’ve hatched. It is important to transfer goldfish eggs into a different tank once you see them for this reason.

Why Do Fish Eat Their Fry?

Scientists aren’t 100% sure why fish eat their offspring. It could be for a number of reasons. They might be eating the fry that lack survival traits, therefore they are increasing the survival of the species. It also might be because the female is replenishing her fat storage. It may also be a reaction to stress in the fish, causing their self-preservation instincts to kick in. There is no reason that we fully know of as to why fish eat their babies.

How Do Fish Feed Their Babies?

Most fry have to find food for themselves, whether it’s small prey or plants and algae. Some fish such as discus produce a slime on their bodies that their young feed off. Some cichlids have been known to take flake foods in their mouth, chew it into little bits, and spit them out for their young.

Do Fish Produce Milk?

Fish don’t produce milk as such, but they sometimes produce a mucus based secretion that coats the bodies of both parents. The babies, once hatched, will find their parents and feed on the mucus secretions that coat their bodies.

How Long is a Fish Pregnant For?

It varies depending on the species of fish. Typically, about 30 days.

Is There Money in Fish Breeding?

If you breed popular or rare fish there is definitely money to be made. However, you won’t make much money unless you have the time and the resources to dedicate to it. There will always be demand for guppies, bristlenose plecos, and platies. People are often inclined to buy their fish from a source other than the big pet stores, because of how often they are diseased and unhappy. Breeding exotic looking fish like blind cave dwellers would also be the good option. If you had the means to breed rare expensive fish, that would be the best idea. Red Frontosa, freshwater stingray, or zebra pleco will earn you a lot of money.


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