Why is My Cory Catfish Floating?

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Corydoras are generally hardy and resilient fish, but they can also experience health problems in some circumstances. There are several signs hinting at the fact that your fish deals with some health issues.

Most of them relate to the fish’s behavior, as the catfish can experience a lack of appetite, irritability, lethargy, hiding behavior, etc.

But, sometimes, sick fish can also display erratic swimming or buoyancy problems, rendering them unable to maintain their body position.

It’s not normal for your catfish to float at the water surface or even in the mid area. So, why is that happening?

Why is Cory Catfish Floating?

The most common cause is swim bladder disorder. The swim bladder is an organ that takes in and eliminates air, depending on the fish’s intentions.

If it fills with air, the fish raises to the water’s surface, if it empties, the fish sinks.

Swim bladder disorder isn’t a condition in and of itself but more of a collection of symptoms, often with multiple triggers.

In essence, we’re talking about infection, physical trauma, or other biological, mechanical, or environmental factors that affect the bladder’s normal functioning.

This renders the fish unable to sink, float, or maintain body position when swimming. So, let’s look at the most common triggers to keep in mind.

What Causes Swim Bladder Disorder in Corydoras?

Consider the following:

Poor Water Quality

Corydoras require clean and stable waters with balanced parameters. While catfish are generally resilient and can adapt to suboptimal living conditions, they will eventually experience health problems.

That’s because there’s a difference between poor water conditions in the wild and captivity.

The aquarium is a closed system that lacks the free circulation of chemicals present in natural, open ecosystems.

So, the accumulated ammonia and nitrites due to the organic matter decaying in the water have nowhere to go. The filtration system will dilute some of the chemicals, but the majority of them will remain in the water.

You need to execute regular tank maintenance to remove them and stabilize the ecosystem.

Ammonia is poison to catfish and fish in general and is responsible for a variety of health issues, including swim bladder disease, ammonia poisoning, and ammonia shock.

Dirty waters also contribute to a higher risk of bacterial and parasitic infections, which are common swim bladder disease triggers.


Infections are common among Corydoras due to the catfish’s sensitive skin and mouth. These fish have soft tissues and lack the protective scales that shelter other fish from harsh environmental conditions.

This is why it’s always critical to house your catfish in a personalized setting with a soft, sandy substrate and safe decorations. Rugged and sharp rocks and even small pebbles spread across the substrate can cause small cuts or abrasions in the fish’s skin.

These can infect fast, allowing the bacteria to reach the fish’s organs and trigger the swim bladder disease.

The risk of infection is even higher in dirty waters, which brings us to the previous point.


Overfeeding is an interesting one because it’s so prevalent among catfish keepers. The more inexperienced ones, at least.

Generally speaking, catfish get much of their food from their environment. So, they don’t need as much food as other fish, especially when housed in a community setup with plenty of other fish species producing a lot of food residues.

Your typical catfish won’t need more than 2 meals per day, with an average eating time of 2-3 minutes per meal. The problem is that most catfish will easily overeat if given the opportunity.

Overeating can cause stomach bloating and constipation but can also lead to swim bladder disease.

This happens due to the oversized stomach pressing against the bladder and causing buoyancy problems as a result.

Low Water Temperature

Few people know that low water temperature is often responsible for swim bladder disease.

The reason for that is the fish’s own biological reaction to the lower temperatures. In other words, the fish’s metabolic rates fluctuate depending on the water temperature. Higher temperatures accelerate the catfish’s metabolism, while lower ones decelerate it.

This wouldn’t be a problem if the catfish living in uncharacteristically low water temperatures wouldn’t also experience slower digestion.

Not realizing this change and feeding your catfish the same amount of food as before is a surefire way of causing digestive problems. Especially constipation.

You already know where this is going. The stomach will inflate and press against the swim bladder, triggering buoyancy problems and even causing death.

Genetic Problem

Some catfish are even born with genetic problems that influence the functioning of their swim bladder. This is a rather rare condition that can occur in most fish species, and it’s most visible at an early age.

This is why you should always handpick your fish carefully to make sure you’re getting a healthy specimen.

Unfortunately, such genetic issues don’t have any reliable solution.

How to Treat Swim Bladder Disorder in Corydoras?

You should first diagnose the problem to make sure you’re on the right track. Affected fish will display symptoms like an inflated belly, lower appetite, curved spine, and buoyancy problems.

Some fish will float, while others will struggle to float, as they keep sinking. They may even display difficulties staying upright and maintaining position during swimming.

Once you’ve diagnosed the condition successfully, consider the following potential treatments:

  • Fasting – This is the first line of attack, given that swim bladder disease is most often the result of overfeeding, poor water conditions, or constipation. All these problems are often responsible for an inflated abdomen pressing against the swim bladder. Force your fish through a fasting period to allow the digestive system to pass on the food. Your catfish will be just fine without food for 48-72 hours.
  • Adjust water temperature – Make sure that the water temperature is within the right parameters. For Corydoras, that’s between 74 and 80 F.
  • Boiled peas – Peas contain many fibers that are great for digestion. Boil some peas, allow them to cool off, peel them off, and crush them for ease of ingestion. You can feed your Corydoras boiled peas for a couple of days to see whether their condition improves.
  • Medication – Antibiotics are also necessary if your cory catfish shows signs of infection. The type and amount of antibiotics to use depends on the type and severity of the infection. I recommend speaking to a professional if you can’t get the doses right.

You can also add a pinch of salt to the tank water and use a conditioner for a plus of protection and improved healing support.

The conditioner will also reduce the fish’s stress, aiding in recovery.

How to Prevent Swim Bladder Disorder in Corys?

I have several tips in this sense:

  • Clean your catfish’s environment regularly to prevent infections and respiratory and digestive problems
  • Keep the water temperature in the ideal range; some fluctuations are acceptable but only minimal and preferably rare. Invest in a heater for a greater degree of control
  • Avoid feeding your catfish dry food; always soak flakes and pellets thoroughly before feeding them to your catfish. Also, crush the larger chunks for ease of consumption
  • Only feed your Corydoras small meals, enough for them to consume within 2-3 minutes at most

Even more importantly, source your Corydoras wisely. Stay away from commercial fish shops if you want to reduce the risk of getting sick fish or one with a compromised immune system.


Corydoras shouldn’t experience frequent health problems, especially if you provide them with a clean, healthy, and stable habitat.

But, if they do, you now know what to do.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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