Breeding Cory Catfish: it’s very exciting and when the parents have done a good job you will have some eggs sitting in your tank. But what to do with them? How can you even be sure they are from Cory catfish? That and much more gets answered in this post.

What do cory catfish eggs look like?

Corydoras eggs have a very characteristic white color with an often visible eggshell. The eggs are 1-2mm and laid in small groups of 10-20 eggs. One to two days after fertilization the eggs turn more brown-orange and small black spots appear.

Cory Catfish eggs are easily distinguishable from other eggs because the female almost always sticks the eggs in small groups of 10-20 eggs on flat surfaces. Eggs are often laid against glass, filters, plants, or wood. So if you find eggs that meet up to all the above criteria, you can be pretty sure your Cory Catfish have been busy…

Eggs of Corydoras sterbai
Eggs of Corydoras sterbai

How many eggs do Cory Catfish lay?

When you’re thinking about breeding cory catfish, it might be beneficial to have an understanding of what you can expect. Will you see hundreds of eggs scattered throughout the tank, or will I have to search through my whole tank before seeing a single one? Luckily, Cory Catfish are way more easy egg layers.

One female corydoras can lay between 10 and 50 eggs per spawn. Some species lay all the eggs at once, while others spread out the laying. Bigger species can lay more eggs and the more conditioning has been done before spawning, the more eggs cory catfish can lay.

It’s important to note that small cory catfish types, like C. pygmaeus or C. hastatus lay less eggs that are smaller. This makes it better to breed them in a smaller tank, where it’s easier to control the conditions.

Conditioning the adults.

When breeding Cory catfish, it’s recommended to condition the parents before you start triggering the spawn. This is done by heavily feeding the parents for two weeks with live foods. This makes the females fat and promotes egg production.

When conditioning the fish to get them to spawn, this has two main advantages:

  • It improves the chances of breeding success. Some species, like albino cory catfish, will not need any incitement for spawning. They will lay tons of eggs with little to no extra effort. Most other species will however need some form of conditioning in order to show breeding behavior.
  • Egg production is stimulated. High protein and fat-rich live foods will cause more eggs to be produced. Some high protein foods you can feed are blackworms, bloodworms, mosquito larvae, and tubifex.
If you want to know whether your cory catfish is a male or a female, read our full guide on sexing cory catfish.

Species

You might have seen a report of huge spawns with hundreds of eggs. This will be most likely of Albino (sp. Aneus) Corydoras. This species is known for laying lots of eggs at once and is very easy to breed.

However, not all species lay so many eggs at once. Corydoras trilineatus for example. They will usually spread out the laying of eggs over the span of multiple days, so there will be smaller clutches of eggs.

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

Cory Catfish eggs Hatching time

On average, Cory catfish eggs take three to five days to hatch. In rare cases, it can take up to seven or more days for the eggs to hatch. The hatching time depends on the species and water conditions such as temperature.

When the eggs are about to hatch, you will see the tail of the Corydoras fry out of the eggs. Don’t worry when you see an egg with a tail, this is just a good sign.

Temperature as variable

Temperature is a big factor when it comes to hatching your corydoras eggs. The warmer the water, the faster the eggs will hatch. The metabolism of animals in warmer water is higher, and thus it will have an effect on how fast eggs hatch.

A study performed on the hatching rate of Channa species (Snakheads) showed that the higher the temperature was, the faster eggs hatched. At around 89-93° F, eggs hatched the fastest. However, less fry survived at these high temperatures. At around 82° F eggs hatched fast and a lot of fry survived. This seemed to be the sweet spot.

Although the study wasn’t about cory catfish eggs it does insinuate the importance of having a good temperature for hatching fish eggs.

For hatching corydoras eggs, the best temperature is 72-78°F. At this temperature, the eggs will hatch fast and fry will develop quickly, without giving infections to much chance to develop.

It certainly isn’t necessary to heat the fry container more than the parent’s tank. In this case, just put the egg container at the same temperature and the eggs will hatch just as good. They might just hatch a little slower.

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Do corydoras eat their eggs?

Breeding Corydoras isn’t an easy task. At least raising the young isn’t. Finding Corydoras eggs is just the beginning of a lot of work, since the parents don’t care about their eggs.

Corydoras Catfish do not care for their eggs and will eat them when given the chance. They will not actively search for eggs to eat them, but when a male or female comes across the eggs, they will eat them. 

How often do cory catfish lay eggs?

Having cory catfish eggs is a nice surprise. If you want to raise the fry, it’s important to anticipate and prepare an environment for the eggs to hatch. That’s why it’s useful to know how often cory catfish lay eggs.

Cory catfish don’t lay eggs on a regular basis, which makes it hard to put an exact number on how often they spawn. However, in optimal breeding conditions you may expect a spawn every 1-4 weeks. Difficult species will only lay eggs after extensive conditioning and sometimes need months to recover.

Caring for Corydoras eggs

After your Corydoras have spawned, it’s important to take some action to ensure the eggs hatch properly. Corydoras aren’t good parents, but luckily hatching the eggs is a straightforward process and you don’t need to buy expensive equipment.

Fertilized vs. Infertilised Cory Catfish Eggs

You might be even looking at some eggs thinking to yourself whether you can expect baby Corydora Luckily, it’s fairly easy to identify fertilised eggs. 

After two to three days of incubation, fertilized eggs will turn darker. Dark brown spots will appear, indicating the growth of the embryo. Unfertilized eggs will not change in color and grow a moldy-like structure.

When unfertilised eggs turn white or get bad, it’s usually said that fungus grows on them. However, in most cases it's not mold, but the result of bacteria feeding on the dead material. These bacteria cause the white fungus-like structure on the eggs.

Fertilized vs. unfertilized Corydoras eggs. © Girls Talk Fish on YouTube.

Eggs with only a female

Female cory catfish sometimes lay eggs without males. This can be due to a temporary state of stress, or out of instinct. When only females are in the tank, the eggs will not be fertilized.

It isn't as obvious as it might seem though. Some species like guppies have the ability to store sperm, so they can produce offspring a long time after mating. Cory Catfish however don't have the ability to do this and can only produce offspring when a male is present during spawning.

Seeing eggs in your tank is therefore not a guarantee that there are males present, or that you’ve had a successful spawn. 

What to do with Cory Catfish Eggs?

You maybe saw some eggs sitting against the glass, or spotted breeding behavior. Woohoo! The most exciting part (at least in my opinion) can begin: hatching the eggs.

To ensure a high hatch rate, use your fingers to remove the eggs from the glass or structure. Put the eggs in a separate container with enough aeration and some antibacterial medication. Change water every day and after 3-5 days the Corydoras fry will hatch.

1. Remove the eggs from your tank.

As stated above, Cory Catfish do eat their eggs. Especially if you keep your Corydoras in a community tank, where not only the parents but also other fish can feast off the eggs, separating eggs is the only way to ensure high hatch rates.

Wait for around one hour after spawning before picking the eggs. The eggs will then be hard enough to take out without being damaged. The eggs are fairly easy to pick easy and not that fragile.

Some people prefer to use their credit cards or even razor blades. However, both might damage the eggs. Using your fingers to gently roll the eggs into a net is the way I found works the best.

2. Set up a separate container

There are different types of containers that work well with Corydoras eggs. Basically, any plastic tub, not too big and not too small will work. Some people prefer to use professional breeder boxes, while others hatch them in a fully separated tub. It’s preferably a tub you can place in the tank since the water needs to be heated. 

Egg tumblers do not work as well with Cory Catfish eggs. The eggs are very sticky, and thus stick to the inside of the tumbler. Regular tubs work just as well, or better and don't cost anything.

Next, add some form of aeration. Apart from highering the oxygen levels, the bubbles create a water flow which reduces the chance of infections harming the eggs.

An air pump works best for this. Just attach an airstone to the tubing and turn it on. Not to hard ofcourse, otherwise the eggs can be damaged. Just enough to create a light flow. 

If you don’t have an air pump, you can try attaching the tub close to the outlet of your tank. Poke some small holes and ensure that a good amount of flow is getting to the eggs. This brings enough oxygen to the developing eggs and reduces the chance of the eggs turning bad.

As a last tip, it’s always good to spread out the eggs as much as possible. This way when one egg turns bad, the chance of healthy eggs getting infecting is lower.

3. Add an antibacterial agent.

To prevent the eggs from molding or turning bad, some extra substance needs to be added. There are a few options often used by aquarists:

  • The most commonly used solution is Methalyne blue.  Add 1 teaspoon of 2.303% Methylene blue per 10 gallons of water.
  • eSHa 2000 is another popular treatment, often used by breeders in  Europe. medicine. Use it three days in a row: add 6 drops per 5 gallons of water the first day. Halve the second and third day to 3 drops.

Another tip: if your filter contains any carbon, make sure to remove it as it will neutralize the medice.

In their wild habitat, eggs are often laid against leaves, which prevent infections. Catappa or Indian almond leaves are thus a great natural alternative to chemical substances. On top of that, Almond leaves cultivate micro-organisms that serve as the first food for the fry.

In fact, I’ve completely stopped using chemicals and switched to catappa leaves instead, which work great! You can check the leaves I get on Amazon.

3. Change water every day

After setting up the container, the work isn’t done yet. If you put the eggs into a separate tub, change the water preferably one to three times a day. This will enhance the development of the eggs and again, reduce the chance of infections.

I have found a good way to do this is by using an air hose. You can very carefully pick out the bad eggs and suck out any waste. Especially when the eggs hatch this will be a very easy way to keep the tank clean.

3. Remove unfertilised eggs

As stated above, not all eggs will be fertilized. Thus, apart from changing water every day you will need to pay some attention to the development of the eggs. In order to protect the good eggs from infection, it’s necessary to pick out the bad eggs every day. These are the unfertilized eggs or the eggs that have developed a white mold-like shine. 

You can easily remove the bad eggs by using tweezers, or by sucking them out with an air hose during the water change.

Where do cory catfish lay their eggs?

Cory catfish usually lay their eggs against the glass, plants or hard structures like wood or stones. Some species also deposit their eggs in the substrate. They will lay their eggs spread around the tank, in small clusters. 

Caring for cory catfish babies

After your eggs have hatched, it’s not over yet. In fact, the fun part still has to come! Raising cory catfish from tiny animals to healthy adults is extremely rewarding.

Here are a few tips to raise your cory catfish successfully:

Set up a dedicated grow-out tank

In order to carefully monitor your cory catfish fry, setting up a dedicated grow-out tank is highly beneficial.

The fry will be able to eat more and have a better environment, causing faster growth.

The ideal size for such a grow-out tank is 20 gallons, but 10 gallons is possible too (if you don’t have too many fish). Bare bottom tanks without much decoration or plants make it easy to clean them.

Feed only high-quality food

This is crucial for raising healthy and strong cory catfish. There are tons of foods available on the market, so it can be confusing. Unfortunately, only a handful of those is actually good foods.

Cory catfish fry will grow the fastest when given a variety of live foods. This includes baby brine shrimp (the best food, period), micro worms, grindal worms, blackworms, etc.

In terms of frequency, it’s important to feed your babies at least two times a day. Preferably even more, because the more you divide your feeding sessions, the more food the fish will be able to eat.

Perform regular water changes

Because cory catfish fry needs to be fed at least twice a day, with high-protein foods, this will pollute the water. I recommend you change the water at least every two-three days. This depends on how much you feed. If you feed more than once a day I recommend changing the water daily to keep the water quality perfect.

A female Bronze cory. Photo by h080

Learn how I successfully raise my cory catfish fry.

Conclusion.

Getting eggs of corydoras catfish is very exciting, but there comes more to it than just waiting for them to hatch. The small white eggs are easily recognizable and are almost always laid against the glass.

The parents will eat their eggs, and without extra care, many eggs will turn bad. To prevent this, it’s recommended to pick out the eggs and put them into a dedicated container. This way fry can also be easily raised. In normal circumstances, Cory catfish eggs will hatch in about 3-5 days, depending mostly on water parameters.

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Read everything about breeding cory catfish