Breeding Aquarium Fish – a Brief Guide

There are many reasons people start breeding fish. You get points in a nationally recognized Breeder’s Award program. Some people think they going to get rich – or at least support their hobby – selling the fish that they breed.

Others do it for the scientific interest and fulfillment of seeing different species procreate. What better way to appreciate the “grander scheme” of life? And how about the ease of teaching the little humans in the household about the birds and the bees? So there are countless reasons for this, but the most important is that breeding fish is fun.

How do you spawn fish?

First, you do some basic research. Read and/or talk to someone who already spawned the species. Find out what kind of species of fish you have. Is it a livebearer or egg layer? What is the best ratio of males to females for that species? What is the best spawning age for the fish? What are the ideal tank conditions?

You also need to find out the best way to care for the fry. Some need to be left with the parents for a while. Others need their parents removed to prevent cannibalism. Some require special foods the first week(s). Others can subsist on average flake foods.

This article is not all inclusive. There are many fish that are considered “odd-balls.” They break the rules and do not fit into any one category. They exhibit one or more unique spawning traits to set them apart from the others. That is why breeding fish is so intriguing to many of us. There’s always another challenge or adventure in the hobby.


You usually can’t tell exactly when these fish have spawned. The male constantly chases the female. The eggs are fertilized inside the female’s body. The male transfers the sperm into her vent with his modified anal fin, called a gonopodium. But, if you know the average gestation period for the species and you watch the female’s developing belly size and shape, you can estimate when delivery will take place. Gestation for livebearers can be from 25 – 45 days. Most, but not all, livebearing female fish have a gravid spot near the base of their tail, which is a sort of window to the developing fry. A day or so before delivery, you can sometimes see the babies’ eyes. Some species get a very square-looking chest right before delivering. The most important reason for knowing all this is to know when to remove the female to a separate delivery tank. Sadly, most livebearers will eat fry. Even their own.

Another trick with livebearers is that females can store sperm from the previous mating for many months. Just because you lost the male doesn’t mean the female will not have any more babies. Also if you want to breed female A with male B, you may have to make sure that she is not with any other males whatsoever. Granted, the most recent male will most likely be the father of the fry. But it is always better to be extra careful with livebearers.

Generally speaking, the delivery tank should be 2.5 – 5 gallons. Use 70% water from the original tank, a sponge filter, and a heater if needed. Live floating plants, or artificial “spawning grass” will give the fry somewhere to hide. Lowering the lights will calm the female. Some theories say you should avoid exposing the gravid female to the air. So use a jar to scope her up and transfer her in water to the delivery tank. As soon as she is done delivering, remove the female back to either the original tank or a recovery tank away from the attention of the male. Some species take up to 3 days to deliver their entire brood. Still, others deliver a couple of fry every 5-7 days. Again do some research.

Most livebearer fry can be fed crushed flake food from the day they are born. But all love baby brine shrimp and micro worms! They are generally larger than egg-layer fry and are free-swimming almost immediately. Therefore, they do not require parental care.


As mentioned before, egg-layer fry are often small and require special foods and/or varying degrees of parental care. Do the research. As far as spawning, these fish are divided into seven basic groups according to their different spawning styles:

Open substrate spawners

This is the most common spawning method, mainly used by cichlids. These fish often form permanent pair bonds. The female lays the eggs on a flat surface, such as a rock. The male works in close proximity with her to fertilize the eggs. These fish are often very good at guarding the eggs and defending the fry. Angels, Discus, Severums, Jack Dempseys, Oscars, Firemouths, Jewel Cichlids, Rainbow Cichlids, Rams, many Aequidens species, Sunfishes, Darters, Gobies, Damsels & Clowns.

A compatible pair must be found. This is best done by raising a group of 6-8 fry to maturity and picking out the pairs as they form. Set them up in their own tank, condition them, watch & wait. If the pairs become regular egg-eaters or fry devourers, you can remove the eggs to be hatched away from their parents.

Although these do not technically hide the eggs like the next category, some will often bury them and move them from place to place in the tank. So don’t think you lost the spawn until well past the time when you should see them free swimming. In addition, although this group are not considered Mouthbrooders, some will pick the fry up in their mouths and move them to a safer territory, especially at night time. Don’t think they are eating the fry until many are actually missing!

Substrate Spawners that Hide their Eggs

Several of these fish also form permanent pair bonds. Most, however, do not; it is the female that takes on the care of the fry. Eggs are usually laid in a hidden area such as a cave, flower pot, or shell. Because of their secretive nature, spawning is usually not observed.

Included in this group are many Dwarf cichlids, Apistogramma, Nanacara, Namachromis, Pelvicachromis, Julidochromis, Lamprologous, Loricaria, Farlowella & Ancistrus. It is interesting to note that the males of the catfish species are the ones that take care of the fry.

Set up a pair with several spawning choices. Feed them well and wait for Nature to take its course. The female will lay the eggs within a cave or under a rock, and the male will fertilize the eggs in unison. Sometimes you guess if spawning has actually taken place or not because the female disappears for about two weeks while she tends to her eggs. She drives the male out during this time. When the fry are free-swimming, she will bring them out and parade them around the tank. Pay attention to feeding whatever the fry require. It is often good to remove the male at this point. In another 3-4 weeks, the female can also be removed.


An easy group of fish to spawn because they protect the fry the most efficiently. Also, they tend to be a very hardy group.

Set up a pair with rocks, gravel, and caves. A few dither fish will help them keep their aggressions away from each other. Feed them well. Usually, the male digs a pit in the substrate. The female, when ripe, will begin the circular spanning dance around the pit with the male. Eggs are laid, fertilized, then scooped up into the female’s mouth. In some African Cichlids, the female tries to “scoop up” the egg spots on the male’s anal fin, thereby ensuring that the sperm has reached the eggs in her mouth. The eggs are incubated in her mouth for about three weeks. She will not eat at all at this time unless the eggs have been lost or swallowed. Wait for about two weeks and move her to another tank. When the fry are old enough, the female will release them and guard them. Often, she can be seen chewing up and spitting out food for them. When danger approaches the fry fly at lightning speed to hide in the mother’s mouth. When the young have been free swimming for about three to four weeks, it is OK to remove the female. Sometimes she will eat them if she is ready to spawn again.

Egg Scatterers

This group consists mainly of those fish we call schooling types: Barbs, Danios, Characins, Tetras & Rainbows. They spawn as they school, scattering eggs all over the tank. The females release the eggs haphazardly; the males follow close behind, releasing sperm at the same time. Amazingly, the two meet, and the eggs stick to whatever they land on. The eggs are usually eaten as fast as they are laid by the spawners and their tankmates.

To successfully save the eggs, set up another tank with lots of plants (plastic or real) or mops. Larger gravel or marbles on the floor also help to catch the eggs. Put in an air stone and a heater, if needed. Introduce a female only, and condition her on quality foods for a few days. One evening, introduce a male. The next morning they should spawn at sunrise. After a few hours, remove the pair. Cover the tank with dark cardboard or towels. The fry will hatch in three to four days. They are very tiny and are often described as slivers of glass on the walls of the tank. They require specialized food (infusoria, APR, etc.) at this stage. In a week or so, they will take live baby brine shrimp, vinegar eels, micro worms, and such. After two weeks they can take powdered flake foods. Growth will then be more noticeable. Rainbows are in this category, but breeders usually remove the eggs and hatch them like mop spawners.

Mop Spawners

Mainly comprised of Killifish, these fish lay their eggs in mops made of synthetic yarn, or in plants. The goal seems to be to hide the eggs. Included in this group are Aphyosemion, Aplocheilus, Epiplatys, Rivukus, Simposonichthys, and the previously mentioned Rainbows. What makes these fish different from the egg-lay scatterers is that their eggs are harder and larger, and they only lay about 20 -30 a day. Corydoras catfish also seem to fit in this group in method, although they lay many more eggs. Typically, they will attach their eggs to anything in the tank including the mop.

The spawning tank setup is simple enough. Hang several mops, and add a sponge filter and a heater if needed. Add a pair of fish. The female will lay the eggs deep in the mop or the plant. The male will then fertilize them. Sometimes they will turn right around and eat them. Another difference with Corydoras is that it is now believed that the female takes the sperm into her mouth and fertilizes the eggs which she is clutching in her pectoral fins while sticking it on the preferred surface.

You must pick the eggs out of the mop daily and put them in a small container with anti-fungal medication added (methylene blue or acriflavine). Store the eggs in a darker place, at the required temperature. They will incubate for 14-21 days for killies and 7-10 days for rainbows. As the fry hatch, remove them with an eyedropper or pipette to another small container or tank with the correct water parameters and some Java moss or similar floating plants. Some can take live food right away, while others need infusoria or APR.

Peat Spawners

This group is made up entirely of Killifish. Cynolebias, Pterolebias, Nothobranchus and Fundulopanchax. These are the fish we hear referred to as “true annual” killies. In the wild, they have adapted to life in correlation with the rainy seasons. They hatch, grow, and spawn before the next dry season comes along, during which their watery world as they know it dries up and they die. The eggs are able to survive in this drying period. When the next rainy season comes along: life anew.

Set up a 5-gallon tank for a trio of fish. In it should be a bowl that contains about 2″ of peat moss. Some people like a slow-bubbling sponge filter and some plants or a mop for the female to hide in. Feed the fish well, but away from the spawning container. The male will display himself above the peat moss. When the female is interested in spawning, she will come close. They will seem to dive into the peat, where they will lay a few eggs and fertilize them. This continues several times a dai for many days.

Most breeders collect the peat and give the fish a new batch about once a week. The peat is gently squeezed and placed into some newspaper, lightly covered with a plastic bag overnight. The dried peat is stored in a zipped sandwich bag, in a dark place at the correct temperature.

Here is where you need to consult the charts in the killifish books for temperature and drying /incubation time. It can take anywhere from 2-9 months! And incorrect temperatures can cause poorly developed fry or low hatching rates.

When it is time to hatch the fry, the parents are most likely dead. Wet the peat, then submerge it in a couple of inches of water in a plastic shoe box. Cover lightly to shade the eggs. Within a few hours, the fry can be seen popping up over the layer of peat. Remove them with a pipette and put them into another shoebox with a few inches of water and some peat moss or a floating plant. after about 24 hours, the peat can be re-dried for another two weeks. Try to hatch more fry. This can be repeated 1-2 more times. Feed the fry often and well, paying attention to water quality. Because these fish live such short lives, they grow quickly.

Nest Builders

As the name implies, these fish build a nest in which to lay their eggs. Fish nests are built with bubbles, mostly on the surface of the water using pieces of plants. The male builds the nest. The bubbles stay inflated because of a special mucus he has in his mouth when he blows the bubbles. The nest builders are mainly the labyrinth fished such as Gouramis, Paradise Fish, most Bettas, and Hoplosturnum Cats.

Set up a separate spawning tank for the pair. A very slowly bubbling, aged sponge filter should be included to culture infusoria for future fry. A couple of snails will do the same thing, along with lots of floating plants. A heater will be needed. Some plastic plants or mops are helpful for the female to hide in. The key to the set-up is an upside-down Styrofoam bowl or something similar, taped to the front of the glass of the tank, right at the surface of the water. There should be some dead air space inside the container.

Put the male into the tank, and do not add the female until he has started a bubble nest and she is ripe with eggs. When all conditions are right, the male will entice the female under the nest. He will wrap his body around hers until she releases a stream of eggs. He releases his sperm at the same time. Then he lets her go. She will remain motionless and sink for a moment or two, but the male will immediately go to work gathering eggs in his mouth and spitting them into the nest. When the female comes to, she will often help. This will continue for several hours. When they are finished spawning, the male will violently drive the female away from the nest. Now is the time to remove her.

The male will guard, fix and add bubbles to the nest for the next three days. When the fry begin to hatch, they will wiggle out of the nest. He will actively catch them and spit them back into place. He should not be fed during these 3-4 days. Otherwise, he might forget his job and begin eating the fry as well.

At the age of 6-8 weeks, the fry will begin to develop their labyrinth organs. Covering the tank with plastic wrap or taping the cracks in the glass will keep the air temperature closer to the water temperature and you will lose less fry.

Some exceptions to the surface bubble nest are seen with the Croaking Gouramis and the Pygmy Gouramis. They build their nests inside a cave, so breeders usually use 2″ PVC tubing pieces for them.

🐠𝙃𝙋 Team
🐠𝙃𝙋 Team
We're just like you - aquarium enthusiasts who love aquatic life! We've been caring for and breeding all sorts of freshwater and marine aquarium fishes, plants, and other pretty little creatures for years. We love sharing our knowledge with other fish hobbyists, and this article you have just finished reading is the best proof of that. You can read more about us here.

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