Cory Catfish Eggs: Hatching Time, Fertilization, Care & More

I remember the excitement of my first Cory Catfish egg. I had just set up the perfect tank and was ready to have some baby Corys to call my own. Unfortunately, I didn’t know what I was doing. Luckily, I gained some experience and knowledge over the years. Now, I am willing to share what I learned.

Here is a summary on Cory Catfish egg hatching and caring:

  • Fertilized eggs will feature a black dot on them.
  • The suitable pH for Cory eggs is 7.0 to 8.0.
  • For hatching to occur, the temperature should be around 82 degrees Fahrenheit.
  • Most Cory Catfish lay eggs every seven days.

As we move forward, I will take you a step by step on what you should do once your Cory Catfish laid her eggs. That includes hatching the eggs, acknowledging how long it will take, and using the right products to adjust the water parameters.

What to do After a Cory Has Laid Her Eggs?

Cory Catfish eggs are a common sight in an aquarium and often go unnoticed. But when you do notice them, they can be pretty worrying to the aquarium hobbyist. When a female Cory Catfish is introduced into a community tank with males of the same species, she will often lay eggs during her time there.

If that happened to you, here is what you can do:

1. Check if the Eggs are Fertilized

First off, you will want to determine if the eggs are fertilized. If the eggs have a point or black dot in them, they are fertilized. If there is no black dot, then the eggs are unfertilized. Also, fertilized eggs will be in a different shape from unfertilized eggs. Fertilized eggs are oval-shaped, while unfertilized eggs are like a teardrop.

2. Place the Eggs in a Separate Container

For ease of management, you will want to prepare a separate container for the eggs. This can be done by just placing the larval stage Cory Catfish egg in a small container of water and floating it off the bottom of your tank. 

This will provide shelter for the eggs from your tank mates and any possible mishaps that may occur. This container would also make it easier to observe the eggs for any possible microorganisms that may be present. But if you’d prefer not to do this, you can just leave them in your aquarium. They won’t cause any harm.

There is not much you need to do to take care of your eggs after you have set them inside a container. Maintain your tank water as usual, and do not disrupt the eggs by doing frequent water changes. 

But, be sure that the temperature of the water inside the container is stable since it will impact the development of the eggs. If you intend to breed more than one batch of fry, then you can move these containers around so that each batch has its own “incubation room”.

3. Observe the Eggs for a Few Days

Watch the eggs for any changes to their shape or color over the next few days. Once the eggs have time to mature, you can then determine if they are fertile (black dot) or not.

If you notice any sign of infection on the eggs, such as grayish coloration, dry patches, or a strong smell, then there may be an issue with your tank water quality. You may want to check your water for possible causes of this infection.

4. Moving the Eggs to the Main Tank

If the eggs appear fine and healthy, then you can move them into your main tank after about four days. Keep an eye on them in your main tank for other signs of infection, like grayish coloration, dry patches, or bad smells.

Sometimes, the eggs may not hatch. This may be a sign that the water conditions in your aquarium are not suitable for the eggs to hatch. You may want to consider adding some chemical additives to your water to help with this problem.

5. Add a Few Hiding Places

Once the eggs hatch, you can go on to observe the fry. However, it is crucial to provide some shelter for the fry. You can do this by introducing some aquatic plants or driftwood into your aquarium.[1] These serve as a good shelter for the newly born fry. 

Also, avoid any filter changes during this period of time in your aquarium. This will help the newborns not get sucked into the filter and killed.

6. Start Adding Food

After about one day, you can start feeding the fry with newly hatched brine shrimp or similarly sized foods. The babies should be eating just fine after about six days (one week). You can expect them to grow into medium-sized (1″ – 2.5″) yellowish juvenile Cory Catfish.[2]

You can also feed the fry with finely chopped fish food or finely diced blood worms. The newly hatched Catfish fry will eat anything they can fit into their mouths, so it’s better not to give them food just too big to consume.

The fry should be fed three times per day after their first week of life, as follows:

  • First feeding at 8 AM
  • Second feeding at 8 PM
  • Third feeding at 8 AM on the following day

How to Adjust the Tank for Cory Catfish Eggs?

Cory Catfish eggs might not survive in your tank unless you adjust the water parameters. Here are some of the general factors that you should adjust in your tank:

1. Water Parameters

If you’re planning on breeding a species of Cory Catfish, you’ll need to maintain the water parameters in your tank correctly. The optimal water parameters for this fish are 7.0 – 8.0 pH, 0 Ammonia, and 3 – 10 degrees dH.[3]

I personally use the API Aquarium Test Kit (link to Amazon) to measure the pH, ammonia, nitrates, and nitrites in my tank. That cost-effective bundle lasts for about eight hundred measures, which is good enough to last me over a year.

To adjust your tank’s water parameters to these levels, you can use chemicals like the API pH UP (link to Amazon). If needed, you can also use the API TAP Water Conditioner (link to Amazon) when replacing the water.

Note: The API products are highly potent, so use them with caution. I’ve had my fish tank running for years now without any issues, but always remember to take adequate safety precautions when using them.

2. Removing Other Fish From The Tank

If you’re planning to breed a species of Cory Catfish, other fish will most likely cause harm to the eggs or fry in your tank. You’ll need to remove any other fish from the tank for now. Otherwise, you risk harming the eggs or the young fish by accidentally bumping onto them. 

3. Hiding Places

When the eggs are about to hatch, you need to provide some hiding places for the newborn fry. A good hiding place for them is a niche between rocks or plants. Suitable vegetation would be Java Moss, other small plants like water sprite or duckweed, and some driftwood. 

4. Oxygenating the Water

Oxygen is an essential element to keep in your mind when breeding Cory Catfish. The eggs need this element for their development, so you will need to supply them with ample amounts of oxygen in your tank.

You can increase the oxygen by using a sponge filter, an air stone, or an air pump.[4] You can also add a bubbler directly inside the tank to allow the oxygen to enter. That will prevent your water from getting stagnant.

Personally, I use the Hygger Aquarium Air Stone Kit (link to Amazon) to oxygenate my tank. All I do is placing that device in the middle of the tank, and it takes care of the rest. Stagnant water might be dangerous for eggs since they don’t hold enough oxygen.

5. Perform Regular Water Changes

Performing a water change is an essential part of maintaining the quality of your tank water. It’s necessary because of all the waste products and uneaten food that your fish produce in their waste.[5]

In the case of breeding a species of Cory Catfish, you may need to perform more frequent water changes to keep your tank free from ammonia. You may also need to use some additives like ammonia remover and pH down for this purpose.

How Long Does it Take for Cory Catfish Eggs to Hatch?

It usually takes three to five days for Cory Catfish eggs to hatch. It may take longer than that if the water temperature is lower than 82 degrees Fahrenheit. In higher temperatures, the eggs hatch sooner. You can tell that they have hatched when the outer membrane has been absorbed inside the egg. 

If you touch the egg and it feels sticky, then it has not hatched yet. When it is ready to hatch, the egg will feel smooth, and you can see the babies moving inside. When the eggs begin to hatch, you may see two or even three babies swimming nearby.

Do Cory Catfish Lay Unfertilized Eggs?

Cory Catfish do lay unfertilized eggs. This is a common occurrence when the female Cory Catfish is introduced to a community tank. A common symptom of unfertilized eggs is that they are always laid on the tank’s bottom and are teardrop-shaped.

The female lays these eggs for several reasons: as an act of aggression (towards another fish), if she has not mated yet, or if she was stressed out and her body is producing more than one clutch of eggs at a time.

How Can You Tell if a Cory Catfish Egg is Fertilized?

You can tell if a Cory Catfish egg is fertile by observing it over the next few days. An infertile egg will usually deteriorate and lose its teardrop shape, while a fertile egg will become more oval-shaped over time. A black dot on the surface of an egg is usually a sign that it is fertile. 

The fertilized eggs will hatch after three to five days, and the babies will immediately begin feeding on tiny plankton. Once they start eating, you may notice small strands of threadlike filaments coming from the mouth of the babies with each bite. The filaments are actually the eggshells of other Cory Catfish eggs that were eaten and digested while the baby fish eats through them.

How Often do Cory Catfish Lay Eggs?

Cory Catfish usually lay eggs every seven days. You can hasten that by adding frequent doses of live foods into their diet, such as brine shrimp. Female Cory Catfish may lay eggs in a week or two without any added food. Generally, they lay eggs in two or three clutches during a breeding season.

During this period, the female Cory Catfish will not eat at all and is often on her own. She will generally lay her eggs in different areas of the tank. This is a way of making sure that some of the fry will survive if she cannot look after them.

Cory Catfish are also not particular about the time of laying eggs. They may lay eggs at night or during the daytime. But since they lay a lot of eggs during a breeding season, it is best to provide them with some shelter and water conditions conducive to their development.

As of last words, here is the equipment I use in my tank to breed Cory Catfish:

Using these will ensure your Cory’s eggs and babies have a nice setup for their first few weeks of life.

References

  1. https://be.chewy.com/aquarium-fish-hiding-places/
  2. https://www.aquariumcarebasics.com/freshwater-aquarium-fish/cory-catfish/
  3. https://www.aqueon.com/information/care-sheets/corydoras-catfish
  4. https://www.ratemyfishtank.com/blog/properly-aerating-your-aquarium
  5. https://www.aqueon.com/articles/dangers-of-uneaten-fish-food

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