So, you’re thinking about breeding your cory catfish? Great choice! It will take however some knowledge to successfully spawn and raise your cory catfish. In this guide, I’ve written everything I can about how you can breed Corydoras catfish in your tank. 

© Keeping Catfish

Best male / female ratio for breeding cory catfish

When breeding cory catfish, it’s best to keep one female to two or three males. This improves the chances of the eggs getting fertilized. However, cory catfish aren’t that picky in choosing their partner. Even if you only have one pair, you can still successfully breed cory catfish.

Getting a pair will probably not be hard. Since it’s recommended to keep cory catfish at least in a group of six, there’s a very high chance you’ll have mixed sexes to start off your breeding project.

If you’re wondering how many cory catfish you should get to make sure you have either one male or one female, here’s a quick table:

Amount of fish
Chances of getting mixed sexes
2
75%
3
87.5%
4
93.8%
5
96.9%
6
98.4%

You get the point :).

The ideal group size

Normally, I’d say the bigger the group the better. In the case of breeding, however, smaller groups tend to work better. 

The ideal group size for breeding cory catfish is 6 to 7 fish, with 2-3 females and 4-5 males. This gives the best results, with the most fertilized eggs. 

The attention of the males will be more focused on a small number of females and vice versa. This usually gives better results.

Overall, breeding in small groups is both more efficient and easier, because you can carefully monitor all the fish. Some breeders will even only breed trios, in small tanks. 

How to sex Cory Catfish

Sexing Cory Catfish
A pair of Corydoras sterbai (female left, male right). Photo by Bill Kasman

Sexing cory catfish is fairly easy to do if you have healthy fish. Your cory catfish do have to be sexually mature. 

On average cory catfish become sexually mature at around 9-12 months of age. This can be faster or slower, depending on the species, its size, and growth rate.

If you think your catfish are old and big enough to be sexually mature, but can’t seem to sex them, heavily feed them for two weeks with a lot of live foods. This will makes your fish fatter and will accentuate the difference between males and females.

Here are three ways to sex cory catfish:

Size

In this case meaning the length of the fish, not how fast they are. Females are usually up to 1cm bigger than males.

This differs per species though, as some small species like C. panda and C. pygmaeus male and female are really hard to distinguish based on size.

A female Bronze cory. Photo by h080

Body shape

This is primarily notable when looking at your cory catfish from above, and it’s one of the easiest ways to tell males and females apart.

Females are way plumper than males. In the case of females, the broadest part of the body will be around or slightly behind the ventral fins. In the case of males, the broadest part of the body situates itself at or slightly behind the pectoral fins.

Fins

This is some of the more advanced stuff. If you can’t seem to find success with one of the above methods, fins are a reliable way to sex your fish.

Pelvic fins – Males tend to have a more pointed pelvic fin. Females have a more rounded, fan-shaped fin.

Pectoral fins – Some species show big differences in the length of this fin, where males have longer and more robust pecs than females.

Anal fins – Males tend to have a more pointed anal fin.

* Please note that this depends on the species. Some species might extensively show this, while others show little to no difference. Do your research on the species you are sexing.

If you want to know more about sexing cory catfish, read our entire article on this topic. 

How to spawn Corydoras catfish

Now we’re talkin’. We’ve finally arrived at the part you were (probably) coming for. 

Setting up a dedicated breeding tank

Before starting to try and actually spawn cory catfish, it’s important to be prepared by setting up a dedicated tank to breed your fish.

This is applicable to those who house their cory catfish in a community tank. Whether you actually set up a dedicated tank is up to you and there have been many successful breeding attempts in regular community tanks. However, by setting up a dedicated tank your cory catfish will have more peace and it will be way easier to monitor them.

Also, you can later use this tank to raise the cory catfish fry.

If your cory catfish are housed in their own tank, this can of course serve as a breeding tank.

Size

Around 20 gallons (a breeder or ‘long’ tank is preferred because cory catfish will live on the bottom) seems to be the sweet spot. 

You can go smaller to something like 10 gallons but this means your group should consist of a maximum of 4 fish. 

In bigger tanks, it can be hard to find all the eggs your cory catfish have laid. It’s also harder to perform the needed water changes in such big tank.

I prefer to keep my tanks bare, without substrate. This makes it easier to keep the tank clean.

Sometimes, cory catfish might also deposit their eggs into the gravel/sand. It’s pretty much impossible to see these eggs, so you will lose them.

 If you do prefer to use a substrate, here are two tips:

  • Use sand. This protects their barbels and they can dig freely in it. Sand is better than big rounded gravel because small fry can also dig in this.
  • Keep a thin layer. This way, the corydoras catfish will be able to sift out the entire bottom and no waste will stack up in the bottom layers.

Filtration

A strong filter isn’t of vital importance in this stage and they like it a bit dirty. If you are keeping up with water changes, cory catfish can live without a filter in their breeding tank.

However, a small filter like a sponge filter is a great addition. This provides your fish with some extra oxygen and filtration. Especially if you plan to house them for a long period in this tank, a filter is beneficial.

Sometimes a filter of which the flow can be adjusted is a great addition. Some species will only get triggered by fast-flowing water with a lot of oxygen (go to conditioning your fish to know more).

Plants / decoration

Plants are great for cory catfish to stick their eggs to and provide necessary natural cover. On the other hand, they do make it harder to find the eggs, so if you plan on picking the eggs out of the tank it’s best to only add some.

If you want to spawn wild-caught fish, live plants are a must. Most wild-caught fish will only spawn in live plants, and often prefer floating plants to deposit their eggs. 

Other decorations such as wood or stones are a great natural cover and some are needed to make the adult fish feel comfortable. Again, with wild-caught fish this is even more important. We cover the best plants for cory catfish in this guide.

Pro tip: use a spawning mop

As an alternative to a lot of plants in an aquarium, professional breeders often use a so-called spawning mop.

You can easily and cheaply make a spawning mop yourself using acrylic yarn and a floating object like a cork. 

What’s practical about such a spawning mop is that you can easily take out the mop with all the eggs and put it in one container. This way you will not need to take out the individual eggs manually (such as scraping them off the glass/plants) causing possible damage. That’s also just way more work :).

Photo by Jennifer Lynx on YouTube.

Lighting

Lighting isn’t important when breeding cory catfish. In fact, cory catfish don’t even like bright light so you shouldn’t make big investments.

If you want to keep plants, put in easy plants that don’t need a lot of lighting such as java moss, java fern, and anubias. A small LED light will do just fine, but you can even decide to not put in any lights at all.

Part 1. Conditioning your fish

This is perhaps one of the most important parts to breeding cory catfish successfully. 

Conditioning Corydoras is nothing more than preparing them to spawn. This is done by heavily feeding them and sometimes changing the tank conditions to “trick” the fish into getting ready and for females to produce lots of eggs.

How much conditioning cory catfish need depends on the species. Some species like C. aeneus (Bronze & Albino Cories) breed easily without much triggering, while other species need extensive conditioning.

Conditioning your fish does take time, but remember: the better and longer you condition your fish, the higher your chances of success you will have. This will also bring more eggs.

Conditioning cory catfish is fairly easy, but it does take some extra effort. 

For 2-3 weeks, feed your cory catfish high-protein live foods. Preferably 2 times a day, if possible. Here are some of the best foods to feed (remember to vary, very important when feeding live foods!):

  • Blackworms

I’ll start with the best food first. Blackworms are often praised because they’re very high in nutritional value and fish love them! Great food (if not the best) for conditioning cory catfish!

It can be hard to get your hands on these worms since they’re still not very common. The best way is to start your own breeding colony.

  • Bloodworms

Bloodworms are also very popular and widely available. They can cause constipation, so don’t feed them more than twice a week.

  • Tubifex

Very similar to blackworms, but can carry diseases which makes them less ideal.

  • Grindal worms

Also very easy to culture worms, but have a lot of fat in them.

  • Daphnia

This type of food contains lots of water (not that nutritious) but is a great variation. You can probably even catch it in a close-by ditch!

  • Brine shrimp (Artemia)

This is especially popular to raise fry (keep reading for more). However, especially the just hatched artemia called “baby brine shrimp” is highly nutritious and is a great power food. 

Part 2. Simulating dry season

In the wild, cory catfish breed in cycles, during the rainy season. Since there are only two seasons (dry and rainy) in the Amazon, we’ll have to mimic the dry season before we can mimic the rainy season.

The dry season is a season of scarcity in the Amazon. Temperatures raise, and there is less water and less food. Many fish die, and they go into survival mode.

Ofcourse, we don’t want to literally starve your fish, but we can recreate this on a small scale.

Fun fact: Did you know the only season many wild caught fish are only caught is the dry season? In this season, small puddles make it easier for locals to catch the fish. In open water, this is pretty much impossible.

To simulate extreme drought, remove 50% to 75% of the tank water. Leave it like this from a couple of days up to a couple of weeks. This obviously depends on how easily your cory catfish will spawn.

During this time, increase the temperature by one or two degrees and take out the filter. You can also take out live plants if you want to go the extra mile.

Since you fed a lot in stage 1, you can choose to not feed at all in this stage or screw back a lot of the feeding. This will make the Cory Catfish go into real survival mode!

I learned a ton from the article on Corydoras.zone. I have never read such a detailed guide about simulating the dry and rainy season! I recommend you read it (after reading this article of course). (Link)

Part 3. Simulating raining season

This is the period where your cory catfish will spawn. After a period of extensive conditioning followed by drought, now your cory catfish will expect a rainy season. 

This will be done by combining the following tactics to “trick” your fish into spawning:

Refill the tank with fresh, softer, and cooler water

The first thing you should do is to refill the tank with slightly colder and preferably softer water.

This imitates what happens in the wild. Cory catfish will live in puddles where the amounts of salt and other minerals will heavily increase, causing a higher pH, KH, and GH. When the rainy season starts, fresh rainwater (with 0 KH and GH) will flood these pools. 

In your aquarium, you can do this by adding RO water or clean rainwater (make sure you get non-polluted water).

If your Corydoras didn’t spawn directly after the first try, keep doing this. 

Start feeding heavily again

While maintaining regular water changes, start feeding your cory catfish back again with the live foods. If you want to go the extra, mile, you can feed things as mosquito larvae. These are numerous at the start of the rainy season!

Increase aeration and decrease the temperature

Most cory catfish are perfectly okay if you turn off the heater, so do this. Put in an air stone and increase the filter (if you have put in one) to max flow rate. 

Other factors that influence spawning behavior

Faster current

After a strong rainfall, you might have seen rivers flowing faster than usual. This is exactly what happens in the wild in their breeding season.

Storms/weather

Primarily a low air pressure indicates to fish that there is a storm coming. Many breeders experience their fish spawning during storms/heavy rainfall

The acidity of the water (pH)

As we discussed above, as the dry season gets to its end, rivers and pools have more dissolved minerals and salt in them (because there is no rainfall). When the rainy season begins, these pools will be flooded with soft rainwater.

Season

Some species will only breed in a certain part of the year because they have a very strong biological clock.

Hormones in the water

Fish breeding in the water causes the other fish to get incentivized to spawn. It creates a sort of chain reaction. Some breeders put in easy breedable fish like guppies in their tank for this reason.

Corydoras spawning/breeding behavior

Corydoras trilineatus in breeding position. Photo by h080

These water changes will usually make the cory catfish go nuts – literally! Don’t stress out if you see your fish swimming throughout the tank, against the glass. This probably means something’s up!

The breeding process usually takes a couple of hours. During this process, the male and female get into the classic “T”-position. The male is at the base and will release sperm, which the female will swallow. During this period, the fish will swim enthusiastically throughout the tank.

Even scientists don’t have fully figured out how they do this, but it’s pretty incredible! Females have found a way to pass the sperm via their digestive system and fertilize the eggs.

Where the female will deposit the eggs, and how much, depends on the species. As dr. Ian Fuller describes, that some species have very sticky eggs, that are laid closely together in a clump. Other species lay less sticky eggs, more scattered around the tank. The latter usually inhabit slower moving rivers, where this is of less importance.

Corydoras aeneus for example lay their eggs all at once, in huge quantities. On the other hand, I’ve found C. trilineatus to lay their eggs not all at once, but spread out across multiple days/weeks. 

Where the fish deposit their eggs also depends on the species. Certain species will only place their eggs against plants, while other prefer sand or glass. 

How to hatch Corydoras catfish eggs

Now that your cory catfish has spawned, it’s time to make sure the eggs will hatch. Overall, there are three possibilities:

  1. Take the eggs out of the tank
  2. Take the parents out of the tank
  3. Do nothing and hope for the best

You should never go for option three, as cory catfish eat their own eggs and fry. This will cause you to lose most fry.

Option one or two are both good choices and depends on what’s most practical for you.

In normal circumstances, the cory catfish eggs hatch between 3 and 7 days. The first days of their lives, the fry will eat off their yolk sack.

A) Take the eggs out of the tank

After the spawning, wait around 1-2 hours before touching the eggs. This will ensure the eggshells have hardened enough so you can safely take them out.

Some people use a credit card or razor blade to do this, but this might hurt the eggs. The safest way is to gently roll the eggs off the glass using your finger. Don’t worry, the eggs are pretty though so none should burst or get damaged. If there are eggs that burst, these were probably not fertile.

A) Setting up a separated container

Before pulling the eggs out of the tank, it’s important to be prepared by setting up a container to hatch the eggs.

You don’t need an expensive egg tumbler, and it’s actually very easy to do. The only things you need are:

  • A plastic container, such as an icebox.
  • An air pump with tubing.

The size of this plastic container isn’t of vital importance, but for practical reasons, I recommend picking a tub around one gallon. You’ll have to change the water frequently, so a small tub makes this easier. Don’t poke holes in it, because then you will not be able to add anti “fungal” medicine.

Create some water movement using an air pump. This will give the eggs more oxygen and prevent infections.

You will need a way to heat this tub. The best way to do this is to put the tub inside your aquarium and attach it to the glass. You’ll also be able to manage the eggs and keep up with their development.

As an extra tip, try to spread out the eggs in the tub. This will make sure that when an egg develops an infection, it will less likely infect other eggs.

Add an anti bacterial medicine to the tub

If you’d just leave it at this, many if not all eggs will start to develop bacterial infections.

To prevent this, there are a few different options:

*Important: as soon as the eggs hatch, these should be removed, otherwise fry might get hurt.

Methylene blue

A medicine that can be used for a lot of treatments. Turns the water blue, hence the name. 

eSHa 2000

An old-school medicine that a lot of people in Europe swear by. It’s readily available, and you can buy it on Amazon.

Hydrogen peroxide

I learned this from Dan’s fish. I never tried it myself, but it seems to work really well. 

Catappa (Indian almond) leaves

I’ve saved the best for last (at least in my opinion). IAL adds a lot of botanicals and beneficial tannins to the water, that have anti-fungal and anti-bacterial workings. It’s also the only natural way of protecting the eggs on this list, making them fully safe for babies.

The IAL will attract small micro-organisms that are a great first food for the fry. Buy on Amazon.

It's often said that bad eggs develop mold. This is incorrect, and it's actually a bacterial infection that is developing. It does look like fungus, hence the confusion.

Change water and remove bad eggs

Daily, you should remove the water out of the tub and add new tank water to it. Keep in mind to keep adding the anti-bacterial medicine you’ve chosen.

You should also pick out eggs (using f.e. tweezers) that have turned white and seemingly developed some sort of fungus. The eggs should turn brown-orange indicating fertilization.

I recommend you don’t throw away these eggs immediately but put them in a dedicated container. There is always a chance you mistook a bad egg, so this still gives the eggs a chance to hatch.

Pro tip: add shrimp to the tub

A great way to decrease the chances of bacterial infections taking over the eggs is by adding shrimp to the container.

Shrimp are known to eat organic material and will clean the eggs. They won’t eat the eggs themselves, only the bad bacteria growing on them. 

I’ve also experimented with snails. They seem to do the job, too. Although I do trust shrimp a little better :).

Source: Delightful Daze on YouTube

B) Removing the parents from the breeding tank

Some breeders use big breeding tanks and prefer to catch out the parents, instead of taking out the eggs. 

This will cause fewer eggs to get possibly harmed by taking them out of the tank. You will also never need to transfer the fry to a new tank causing possible outfall. 

The disadvantage of using this method is that it’s harder to supervise the eggs or feed the fry as opposed to a small container. Fry might not find food as easily.

Caring for the eggs/fry is exactly the same as caring for them in a small container, only on a bigger scale.

As you can see, Corydoras can lay lots of eggs.

Read everything about hatching cory catfish eggs, from A-Z.

How to raise cory catfish fry (babies)

After three to seven days, the eggs will be hatched. Raising the fry can be challenging and especially in the first days, they’re very sensitive!

Food

Feeding your cory catfish fry is crucial to make them grow fast. The food you feed should be high in protein since cory catfish are carnivorous fish.

Important: the fry doesn’t need any food for the first 24-48 hours of their lives, because they live off of their yolk sack.

I’ve written down the best foods to feed your cory catfish fry. I recommend you vary between different foods. This will make sure the fry has all the nutrients they need.

Powder foods

Time frame: directly after consummation of yolk sack

Powder foods are very convenient to use, which makes them a food choice for people that don’t want the hassle of breeding live foods. Fry can sometimes have difficulty eating this food, as opposed to live foods.

A great small product for cory catfish fry is Hikari first bites. This is designed specifically for baby fish so you can be ensured to feed the right foods. Buy Hikari first bites on Amazon.

Micro worms

Time frame: directly after consummation of yolk sack

Micro worms are the best food to give newly-hatched cory catfish. They’re extremely small, making them easily edible for the fry. 

Egg yolk

Time frame: directly after consummation of yolk sack

Egg yolk isn’t as known as the other foods on this list, but it’s a very nutritious, cheap, and easy alternative.

Just boil an egg and feed the cooked yolk (stirred up in some water).

It does make the water very messy, so make sure to do a water change after feeding.

Baby brine shrimp

Time frame: 1 week after hatching

Baby brine shrimp are the best food to feed to cory catfish fry. Right after they hatch, they’re extremely nutritious and they’re the perfect size food.

Culturing baby brine shrimp does take some effort, but it’s certainly worth it, because you’ll fry grow way faster!

Frozen / live chopped up foods

Time frame: 3-4 weeks after hatching

After 3-4 weeks, you can start giving the fish the foods you’d give to your adults. Chopped-up frozen and live foods such as mosquito larvae, bloodworms, and tubifex are great.

Dried foods

Dried foods are also great for rasing cory catfish. The benefit of dried foods, as opposed to frozen/live foods, is that they are more balanced in nutrients.

If you choose to go with dried foods, you really have to pick a high-quality option. Cheap options have the opposite work and contain lots of fillers and less protein.

I’ve found Bug Bites to be working well, as well as the earlier discussed Hikari First Bites.

How much to feed cory catfish fry

The more you feed the better. Not quantity-wise, but how many times a day you feed. 

Two times a day should be the minimum, but you can go upwards of 6-8 times for optimal growth. The more you spread out feedings, the more cory catfish will be able to actually ingest. Keep in mind that the more you feed, the more you’ll have to change water.

Tank

After the cory catfish have grown a little bit in their hatching container (age 1-2 weeks), it’s time to transfer them to a bigger tank.

This will give them the space they need to develop fast and grow big.

I don’t recommend placing them with their parents just yet. They’re still too small and fragile. Putting them into a dedicated tank makes it easy to feed them and to do lots of water changes.

As of size, around 20 gallons I find optimal. Preferably keep it bare-bottom, this makes it easy to keep the tank clean. Add some plants as cover, and optionally some hard structures.

As for filtration, put a moderately strong filter on it that does 5-10x the volume of the tank an hour. Combined with regular water changes this will keep the water quality optimal for growth.

Water changes

How many water changes you should do depends on how much you feed to the fry.

As a baseline, I’d recommend changing 50% of the water 2-3 times a week. If you feed more than 2 times a day, start changing the water 4-5 times a week or even daily.

Photo by Imseong Kang

Read everything about hatching cory catfish eggs, from A-Z.

Breeding Cory Catfish in a community tank

If you don’t have a dedicated breeding tank available, you can perfectly breed cory catfish in a community tank, too.

Breeding cory catfish in the community tank is possible. The success rate will be lower because other fish might eat the eggs and it’s harder to trigger the fish to spawn in a community tank. Pick an easy-to-breed species like C. aeneus to have the highest chances of success.

Breeding cory catfish in a community tank is fine if you don’t want to dedicate a lot of time and effort to raising the fry. You will have a bigger fallout if you decide to raise the fry in the community tank.

Other fish might have difficulty adapting to the conditioning and triggering process you might want to perform. Species like albino cory catfish or peppered cory catfish are very easy to breed, making them the best choice for a community tank and won’t need a lot of conditioning.

Crossbreeding

Do you keep multiple cory catfish in the same tank? Then you might risk your cory catfish crossbreeding with each other.

Within the genus of Corydoras, there are 9 lineages. Only species that are within the same lineage, the fish can crossbreed.

Source: Alexandrou, Markos & Oliveira, Claudio & Maillard, Marjorie & McGill, Rona & Newton, Jason & Creer, Simon & Taylor, Martin. (2011). Competition and phylogeny determine community structure in Mullerian co-mimics. Nature. 469. 84-8. 10.1038/nature09660.
Source: PlanetCatfish.com
Source: PlanetCatfish.com

As you can see, both Corydoras sterbai and Corydoras trilineatus are part of lineage 9 (In9) meaning they can, in theory, interbreed.

Crossbreeding is always discouraged and should never be done intentionally. You only create hybrids that might end up messing up species!

Conclusion

Are you still with us? Great! This has become a long post, so it’s time to recap.

Breeding cory catfish is fairly straightforward. It depends on the species how hard it is to make a cory catfish spawn. Overall, we can use a method that can be made as extensive (again, depending on the difficulty of the fish) as preferred.

1. Spawning the cory catfish

Certain species spawn very easily, while others need a long process to make them spawn. There is a three-step process you can apply to make your cory catfish spawn.

1.1 Conditioning

Heavily feed your fish during 2-3 weeks with live foods. The fish will put on weight and the female will start to create eggs.

1.2 Imitating the dry season

Lower the water level of your breeding set up to around 25-50%. Increase the temperature a little bit and decrease feeding. Do this from a couple of days up to a couple of weeks. 

1.3 Imitating the rainy season

This is the season in which cory catfish naturally spawn. You imitate this season by refilling the aquarium with slightly cooler water and starting back by feeding lots of live foods. This while decreasing the temperature. Optionally, you increase the flow and add an airstone.

If the initial refill of the tank didn’t work, you keep changing water daily and heavily feeding.

2. Hatching the eggs

The female will have deposited the eggs against the plants or glass. Gently take them out using your fingers and put them into their own container, with an airstone.

Add an anti-bacterial medicine such as Methylene blue or Indian almond leaves, to prevent the eggs from infecting.

After three to five days, the eggs will hatch.

3. Raising the fry

For the first two days of their lives, the fry will live off their yolk sack and doesn’t need any food. 

Start feeding micro worms or small powder foods. After a week of this, you start feeding baby brine shrimp. When the fry is around one month old, you can start feeding copped-up frozen and live foods.

I recommend raising the fry in their dedicated grow-out tank of +- 20 gallons. This will make it way easier to perform regular water changes and for the fry to eat enough.