How To Breed Killifish?

Seeing a fish grow up in front of you is a magical experience. You can breed your mature killifish to be able to witness this process.

How to breed killifish? Put together a male with several females in a big aquarium. Add a suitable breeding box. That’s all! The fish will now breed without any fuss at all!

Breeding is easy but the process that leads to breeding and the effort that goes into it after the eggs have been laid is a bit tricky. Here’s everything you need to know in order to breed your killifish successfully!

Breeding types

Expanding your killifish family will need you to be aware of the different types of killifish.

Mutation and cross-breeding has led to numerous killifish types which are mostly known by their scientific names. There are around 1300 types of killifish. However, as a pet owner, it is enough for you to know about the two broad types.

These two species are:

  • annual killfish
  • non-annual killifish

Annuals, as the name suggests, live for a year only. These killifish originate from areas that have distinct wet or dry seasons. Annuals like hard, alkaline water to live in. You’ll find them mostly in Africa.

During the monsoons season, they live healthily and lay eggs. As the dry season approaches, they die as their streams dry up. However, their eggs stay safe in the mud. When the next monsoon season comes around, these eggs hatch, and the species continues.

On the other hand, non-annuals live for 2-5 years. They prefer slightly acidic water. Non-annuals are mostly found in shallow streams. You’ll find them in rainforests in the natural habitats.

Identifying males and females

The first step in breeding killifish is to form a couple. This can only be done if you can identify a male from a female.

Generally, the major differences are:

  • The males are more colorful and vibrant
  • The females are very plain looking, sometimes even colorless.

The yellow, blue, green, and red killifish are usually males. The females will be of dull colors. This is enough knowledge if you’re planning on breeding.

Place one of the brightly colored killifish with plenty of the dull-colored ones. The rest can be left on the killifish!



Killifish pair up very easily. They don’t have a very long lifespan. Most killifish live for 1 or 2 years only. This is why they quickly mate with any other killifish that is around them.

Such a short life gives the females little time and choice in choosing a partner. Within a short period of time, killifish can mate with multiple partners to lay the maximum amount of eggs possible.

If you’re feeding your fish live food, they’ll gain sexual maturity by the time they get 2 months old.

You may be wondering: what male to female ratio is perfect for breeding?  If you’re trying to encourage breeding, put one male with numerous females. Use a big tank to accommodate all these fish.

Once you put in a breeding bowl in the aquarium, the mature killifish will go ahead and breed on their own. The only thing you have to do is ensure that the male in the aquarium is fully matured.

The male will start showing off his colors to attract the females. Interested females will follow him into the breeding bowl. Here, you’ll notice the pair digging their bodies into the peat moss.

After a few minutes of staying still, you’ll notice a jerk like motion. This will indicate that the egg has been laid. One female killifish can lay up to 30 eggs in one day.

Breeding bowl

Providing a breeding space is a major factor in the entire breeding process. If a specific space isn’t provided, killifish will lay their eggs in the gravel of your aquarium. If you don’t want such a mess, here’s what to do.

You’ll need:

  • A breeding bowl
  • Peat moss

Using a plastic tub is the most convenient breeding bowl. You can get it ready very easily. Use a tub with a lid, such as an old ice cream tub.

Also, purchase peat moss from any supermarket or nursery. Confirm that you buy peat moss and not just simple peat.

First of all, you’ll take the lid and cut a hole in it. A diameter of about 5 cm is enough. Roughly, calculate the size of your fish. This hole should be big enough that the fish can go in and out without hurting themselves.

Now, take the peat moss and boil it. This will sterilize the peat moss and remove any bacteria. Before adding it into the plastic tub, let the peat moss cool down. Put it under running cold water to bring down its temperature.

Some killifish lay the eggs over the pear moss, just slightly dug in. On the other hand, other killifish like to dive in and dig a deep space so that their eggs are secure. Peat moss will be suitable for both these types of fish.

Once you line the breeding bowl with peat moss, add in water. As a precautionary step, add in 2 tablespoons of salt. This will prevent the growth of velvet in the breeding bowl. Also, add in a couple of rocks at the bottom so that the box doesn’t float in the aquarium.

Before you put the bowl inside the aquarium, make sure that all of the peat moss is soaked. This will minimize the mess caused later on. Once this is ensured, gently put down the bowl in your aquarium.

You’ll notice parts of peat moss floating out of the breeding box. This isn’t something to worry about. Once the killifish start moving in and out of the bowl, there will be a lot of mess. Let it be and clean it all at once after the breeding process is successfully completed.

How to hatch killifish eggs

Once the killies have bred, you’ll have to offer some assistance. To make the process easier, safer, and quicker, you’ll need to provide circumstances that will help hath the newly laid eggs.

The eggs have to be incubated in order to hatch healthily. The peat moss that you use in the breeding bowl will serve this purpose. Considering that peat moss is the surface and the temporary is kept at an average of 29 degrees Celsius, the eggs will take 6 to 8 weeks to hatch. In the case of non-annuals, the eggs may even hatch as soon as 2 weeks.

To maintain a consistent temperature, you can use a foam box around the peat. The peat with the eggs should be placed in a dark place. Once the eggs are ready to be hatched, you’ll start noticing that the eggs have started looking like eyes. This is the biggest indicator of fully developed eggs.

In case 8 weeks have passed by and the eyes aren’t appearing, you can still move on with the hatching process if you’re convinced that the eggs are developed.

Do not separate the eggs from the peat. The peat is a requirement for the hatching process. You’ll start by wetting the eggs. For this, take a 5 cm deep tray and fill it up with water. You can either use tap water or the better option will be to use water that is prepared for the fish tank.

Put the peat in this tray and let it soak. With a soft hand, start breaking the lumps apart. This will speed up the process of soaking the peat. As the peat will soak up water, it’ll start drowning to the surface.

Meanwhile, keep removing any debris that floats on the water surface. If the water becomes too dirty, you won’t be able to spot the eggs. However, remove the debris carefully, making sure you’re not removing any floating eggs with it.

As the peat starts drenching, the egg hatching process will start. If everything goes ideally, you’ll start noticing hatched fry within a couple of hours. Otherwise, it may take up to 2 days.

Do not throw away this peat moss. Instead, dry it and keep it secure. There is a possibility that some eggs wouldn’t have hatched. You can dampen the peat moss after a week again to hatch the remaining eggs.

At first, the fry won’t be able to swim properly. You’ll only be able to identify them due to their gentle wiggling motions over the peat. Do not disturb the fry at this point.

Once you notice that the fry have learned to swim a bit, you’ll transfer them to another tray. This is where they’ll grow for the next 3 weeks. Line this tray with Java or Christmas moss. It will provide cushioning and warmth.

The moss encourages infusoria. You can also add a couple of snails in the tray. Their waste also serves as infusoria. Adding a few drops of liquid fry will also boost infusoria production.

Transferring the fry must be done with a lot of care. Use proper tools. You can opt for:

  • An eye dropper
  • A turkey baster

Never opt for a net to transfer the fry. Use a very gentle hand. You don’t want to kill or traumatize the fry during the process.

Do not put in too many fry in one tray. Overcrowded spaces can cause the death of fry. Also, mark each tray with the date of hatching and other details.

Looking after the fry

Breeding will only be fully successful if the fry raise to healthy fish. After you have transferred the fry into a ‘raising tray’, you have to look after them for 3 weeks.

The tray doesn’t require any filtration or aeration. You also don’t have to cover the tray because the fry cannot jump. The fry will stay happier in the same old water that they are familiar with. However, you will have to add more water as the fry grow. You may also have to change the water when it gets dirty.

For this, don’t add water directly from the tap. Let the water sit in a bucket for 2 to 3 days before putting it in the tray. While cleaning the tray, also remove any dead fry that you spot.

After every few days, you’ll notice a layer of oil on the tray. You can remove this by slightly placing an absorbent paper on the water surface. Also, keep the tray away from sunlight. Excessive heat may kill the fry.

Keep the tray as calm as possible. Do not move it around a lot. Avoid any disturbances, especially in the water. Slightest water changes can cause the fry to die.

In these three weeks, you must only feed the fry once each day. Overfeeding can lead to bacterial infections and death.

Bottom line is: your fry won’t starve to death but overfeeding can definitely kill them.

In the second week, you can start feeding high-protein foods. This will compensate for the increased activity in the young fish. At 3 weeks, your fish will be ready to be added to an aquarium with other fish.

If you’re afraid that the other fish species might bully the young fry, you can keep the young ones in a separate tank. This can be a small tank since the young fish cannot jump out and don’t need a lot of space. Add some plants, your killies will definitely appreciate them.


You cannot expect your fish to breed successfully unless they’re in a healthy condition.

A balanced diet will: encourage a healthy breeding process and help the fish reach sexual maturity quickly.

Adult killifish love brine shrimp. It has a high nutritional value. Since brine shrimp grow in salt water that’s acidic, it is free of bacterial infections. You can easily find frozen brine shrimp in the markets. Make sure not to overfeed this food.

Mosquito larvae is another favorite of killies. You can purchase them or culture them yourself. The latter isn’t recommended because if all the larvae aren’t consumed quick enough, they will turn into mosquitos.

Blackworms are a great food option and can be easily bought from fish farmers. They may be carrying bacterial infections so before feeding them to your fish, wash the worms under cold water and refrigerate them. This will kill any bacteria.

Tubifex worms are also a favorite of killifish. These worms can be found in dirty areas such as sewage pipes. Otherwise, you can also buy them. There is a risk that these worms may transmit diseases but, washing the dead worms under cold water minimizes the chances.

A very common live food fed to fish is daphnia. This food serves as a laxative. You can artificially culture daphnia yourself. But, if you don’t have that much time on hand, you can purchase them from a supermarket. Do not feed daphnia exclusively. Mix it up with other options to provide a healthy balance.

Dry foods aren’t the killies’ favorite but you can train them to like them. Dry food is easily available. It is a generous source of vitamins.

Feeding the fry

Once the eggs are hatched, you must start providing adequate food.

Here’s the deal: food for the fry must be something healthy so that the fry grow quickly. But, the risk of feeding a food that isn’t fry-friendly is a risk you must never take.

Infusoria is the perfect feed for tiny fry who cannot eat anything else. If you’re culturing infusoria yourself, do so in small quantities. This is because they go bad within a week.

Your fry will also love freshly hatched brine shrimp. Of course, it’s only fresh if you’re hatching the brine shrimp yourself. It is a suitable food option for the first few weeks after the fry has hatched.

Vinegar eels are tiny worms. They grow in vinegar, hence the name. They are actually easier to culture yourself than to purchase. Before feeding them to your fry, make sure you thoroughly rinse off the vinegar.

Grindal worms can be added to the diet of the fry when they’ve grown for a week or two. If you’re buying these worms from the market, you’ll have to sterilize them to kill any mites. These worms grow in the soil so the risk of contamination is high if not sterilized properly.

Related questions

What is infusoria? Different types of single-celled organisms are categorized as infusoria. They serve as food for young fry. These organisms are naturally present in ponds and lakes. However, for your fry in the aquarium, you’ll have to culture them.

Can you keep different types of killifish together? Yes, you can. Killifish aren’t fussy about tank mates. This quality contributes to the wide range of species of killifish as they easily breed with the different types as well.

What temperature does killifish require? Killies like warm environments. A range of 72 to 85 degrees Fahrenheit is suggested. You can use a heater to warm the aquarium water. Just make sure that whatever you use, it doesn’t cause water movements as killies prefer calm waters.


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