Why Is My Cory Catfish Breathing Fast? {Should I Be Worried?}

Are you concerned about your cory catfish breathing heavily or rapidly?

What happened that is causing this?

In this article, we’ll find out why so we can alleviate the symptoms of rapid breathing and make sure nothing worse happens.

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Why Is My Cory Catfish Breathing Fast?

Cory catfish are sensitive to anything that disturbs their peaceful nature. Too many males, aggressive tankmates, lack of oxygen, obstructed gills and even the the type of substrate can cause them to breathe fast.

Step by step measures to solve these issues will aim to restore the normal breathing patterns of your cory catfish.

Are Cory Catfish Sensitive?

Cory catfish can feel vibrations in and out of the tank. A simple bump or tap on the glass could jolt them and cause their heartrate to jump momentarily. If someone bumped the corner of the table or base of the aquarium, it could stir them up emotionally and make them breathe fast.

This is not true for all cory catfish. Just like humans, different fish display unique tendencies or characteristics to surrounding stimuli. Some are more hyperactive while others are more relaxed. Some hide more and others enjoy roaming around the tank comfortably.

Top 10 Reasons Why Your Cory Catfish Are Breathing Fast

  1. Aggressive tankmates and bullying
  2. Hypoxia – lack oxygenation
  3. Hypersensitivity to nitrates
  4. Not enough hiding places
  5. Too much light
  6. Too many males
  7. Bloating
  8. Gill irritation or illness
  9. Lack of variety and nutrients in their diet
  10. Rough or jagged substrate 

Is My Cory Catfish Being Bullied?

Cory catfish are relatively peaceful bottom dwelling fish. They do not initiate aggression towards tankmates who aren’t trying to chase or bully them.

Unfortunately the same is not true for the type of tankmates you may have chosen to accompany your cory catfish. Even a betta or tetra can feel the need to defend its territory and dart around, fin nip or chase your cories.

A sudden burst towards your cory catfish can leave it strained, startled and in need of a breather. You may notice the corydora sulking or breathing fast at the bottom of your tank for a while. See if this rapid breathing persists to determine if there are more factors at play.

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Is My Cory Catfish Struggling to Breathe Because Of The Water Conditions?

Check your water parameters once more to make sure of the following:

  • Ammonia and nitrites: 0ppm
  • Nitrates: Less than 20ppm
  • pH: Between 7.0-8.0
  • Alkalinity: 54-180ppm
  • Water temperature: 72-80°F
  • Water changes: 10% weekly or 25% every 2 weeks

These figures are subject to criticism or dispute, but the general consensus remains solid. You can be off by a degree or two, but you must check these parameters often to make sure we can cross off these important factors from the list of why your cory catfish is breathing fast.

Hypoxia is referred to the lack of oxygenation. A properly working filter, air pump and the option of adding air stones with help aerate the water to promote healthier breathing patterns are suggested. Please refer to our guidelines for water changes at 10% minimum per week and increase this amount if heavy breathing persists.

Do Cory Catfish Like To Hide?

Imagine being chased or exposed to large amounts of light. Our instincts could be similar to a cory catfish looking for a place to hide. They do not like persistent light and prefer to determine how much light they receive by hiding or finding shade when they see fit.

Plants, caves and decorations give cory catfish plenty of opportunities to hide when they feel stressed, panicked or sensitive to light. Without hiding places, you may notice a cory catfish exposed at the bottom of the tank, breathing heavily with no place to go to calm down.

Do I Need More Female Cory Catfish?

It’s important to manage your ratio of male to female cory catfish.

  • 3:1 
  • 3 females to 1 male

Males are smaller in size and female are rounder. Males chase each other to prove their worth to females. They are more lively and it may cause them to be out of breath from time to time. Too many males stress out the females as well. Add more females to calm things down.

Is My Cory Catfish Bloated?

Your cory catfish might be sighing and resting with heavy breathing to force digestion. They could be straining themselves to force excretion. You may also notice surface gulping where they swim up to the top for a breath of fresh air.

This is normal and could be alleviated by reducing the amount of food or varying their diet. Take a day off feeding to see if that could give your cory catfish a gut rest. Add more frozen or live food such as bloodworms or brine shrimp to their regular diet.

Corydoras move rapidly sometimes because they tend to get hyperactive to surrounding conditions. Doing so with a belly full of food will cause more strain and get them winded easily. They could be breathing fast because of this.

Is My Cory Catfish Sick?

Rapid breathing could indicate that your cory catfish is sick. Obstructed breathing could occur if the gills are impacted with flukes, ich or other parasites. Look out for the following:

  • spots
  • fungus
  • frayed fins
  • split fins
  • barbell loss
  • loss of color
  • bloating
  • red gills

Resort to treating the tank only if you see these conditions getting worse. Melafix is one such treatment, but we recommend consulting with a professional and performing water changes before treating your cory catfish that is breathing fast without any obvious physical signs on their bodies.

Does The Substrate Affect Cory Catfish?

Cory catfish can harm their barbells when they rub up or dig into jagged or rough substrate. Many cory fish keepers suggest smooth gravel or sand substrate instead of rocks that could be harming their barbells. This is not a consensus agreement and we don’t suggest removing your entire substrate and switching it for sand right away.

Look to remove any jagged rocks or anything that isn’t smooth. Cories dwell so often at the bottom of the tank, so they are most susceptible of being affected by the substrate’s physical conditions along with the sulfides and harmful bacteria residing within. Vacuum or use a siphon hose weekly if possible.


We hope you and your cory catfish are more relaxed now. We wish the best for the health of your fish and will do our best to inform you with any knowledge we find useful to you. See you soon with any other fish related questions or concerns.

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.