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Why You Have A Bloated Cory Catfish And How To Fix It!

There are a number of popular types of Corydoras catfish kept within the fish keeping community and their popularity just keeps on growing year after year as more and more people add a cory to their tanks.

Although it is generally easy to care for most types of cory, there is one problem that we see people having issues with time and time again and that is a bloated cory catfish.

Due to problems with a bloated cory catfish being so common as well as potentially lethal, we have decided to publish this article going over the topic as best we can.

Our hope is that we will be able to help as many of our readers as possible better understand the reasons that their cory has bloated up as well as how they are able to potentially treat the issue.

Is It Normal For A Cory To Bloat Up?

The first question that we are going to answer is whether or not it is actually normal for a cory to bloat up.

Although it might seem like something that would be pretty rare, the truth is that bloated cory catfish are unfortunately, quite common, especially amongst people new to the fish keeping hobby.

It is not normal for a cory catfish to be bloated though and a bloated cory is a warning sign that there is a problem that needs fixing.

Unfortinatley, unlike some of the other common problems with fish, if the bloat in your cory is due to dropsy then the odds are definitely against you and there is a high chance that your cory will die within days.

How Can I Tell If My Cory Is Bloated?

There are a number of different ways that a cory catfish can be bloated depending on the cause of the bloating.

The general rule of thumb is that a bloated cory catfish will usually look as though its full body or at least a specific section of the cory is larger than usually.

Depending on whats actually wrong and how developed the problem is, the bloating may only be small but in some cases, it can be obvious that there is a problem with the cory bloating up.

What Causes A Cory To Bloat?

There are five main reasons that you may have a bloated cory catfish that we will be taking a look at below. We have tried to arrange the causes of bloat in cories by descending order of severity.

For example, a cory that has dropsy is far more likely to die than a cory that has bloat due to constipation.

Depending on your level of experience of keeping fish, it can also be difficult for you to be able to workout exactly what is causing the bloat making it harder to get the right treatment!

Still, here is a breakdown and overview of the five most common causes of bloat in a cory catfish.


Dropsy is a condition that can affect fish of all shapes and sizes and unfortunately, it is one of the most serious cause of a bloated cory catfish.

Dropsy is an infection that will cause the cells within the fish to swell up which in turn makes the fish look bloated. The appearance of the fish can be similar to a pinecone and many people refer to the general appearance of the fish as “pineconing”.

The main symptom of dropsy is bloating but there are other symptoms that you may see as well which include a lack of appetite as well as lethargy.

Unfortinatley, it is very difficult to treat dropsy and even if you are able to get a suitable treatment, dropsy can prove fatal to your fish within days so it is very difficult to treat the issue.

The main causes of dropsy include:

  • Poor water quality.
  • Infection, such as a bacterial infection.
  • Parasites.
  • Stress.
  • Genetics.

Due to the severity of dropsy, how quickly it takes hold of the fish and developed as well as the high fatality rate, prevention is definitely better than cure in this case!

Swim Bladder Disease

The swim bladder is a gas filled sac that helps the fish to stay buoyant and in the correct position within the water column.

Swim bladder disease is a condition that will cause problems with this sac which in turn can lead to a bloated cory catfish.

If your cory catfish if bloated due to swim bladder disease then the bloat will usually just be centrallised around the middle of the fish rather than all over like dropsy.

Thankfully, swim bladder disease is much easier to treat in fish and provided you catch it early, you can usually treat your cory and have it return to full health in no time.

The most common cause of swim bladder disease is due to the fish eating too much, eating too quickly, constipation (covered below), and gulping air when eating floating foods. In some cases, unsuitable foods can also cause gas that can also result in swim bladder disease too.


One of the most common causes of a bloated cory catfish is constipation and this is usually due to a diet that is low in fibre.

A high protein diet can often be the cause of constipation as well as eating food that is too large for the cory to eat.

If your bloated cory catfish is constipated then the bloated appearance will usually just be centralised around the ventral side (belly) of the fish.

A bloated cory that is constipated may also have problems with buoyancy as well as swim erratically due to the discomfort that constipation can cause.

An bloated cory that is constipated will also often stop eating and become lethargic.

The good news is that constipation in a cory catfish is usually very easy to treat and provided you make some changes to the diet of your fish, you should see an improvement within a few days.

A Blockage

Due to a cory catfish eating most of its meals from the substrate of your tank, they can sometimes accidently consume parts of your substrate.

Larger options such as gravel or pebbles can then end up causing a blockage in the fish with this sometimes being very difficult to actually treat in the fish.

Just like with dropsy, prevention is definitely better than cure with this one and using a suitable substrate is always recommended.

Internal Parasites

Internal parasites are another fairly common cause of bloating in cory catfish and these are usually worms that can range in size from very small to fairly large.

If your cory catfish is bloated due to internal parasites then the bloated appearance will usually just be centralised around the ventral side (belly) of the fish.

A bloated cory that has internal parasites may also have a loss of appetite, become lethargic as well as scratch themselves on objects within the tank. In some cases, you may also see parasites in the poop of your cory too.

Internal parasites are usually easy to treat but it is worth noting that they can be re-infected quite easily so you will need to take care to prevent them from becoming infected again.

Eggs Ready To Spawn

If you have a female cory catfish that is bloated then it is possible that the bloated appearance is due to her being full of eggs and ready to spawn.

When female corys are ready to spawn, they will often become bloated in appearance as well as become much more active than usual.

If your bloated cory catfish is a female and you think she is ready to spawn then it is worth setting up a breeding tank for her.

Once the eggs have been laid, you can then remove the female cory from the breeding tank and raise the fry in there.


As you can see, there are a few different reasons why your cory catfish may be bloated but thankfully, most of them are quite easy to treat.

The best thing you can do if you think your cory is bloated is to keep an eye on him and look out for any other symptoms that may be present. As we covered above, there are a number of different potential causes of bloat in a cory catfish with each having a different level of severity.

Unfortinatley, some of them can quickly prove lethal for your fish where as others are very easy to treat provided you catch them early enough.