Why Is My Cory Catfish Turning White / Pale?

Last Updated on August 1, 2022 by cmoarz

It sucks when you witness your beloved Cory catfish turning white or pale. There could be a number of reasons behind it, Some that are harmless and others that are more serious and might even be fatal to your fish. In this article, I’ll go over some of the more common causes and what you can do to help your fish.

New fish syndrome

New fish syndrome is the most common reason for a cory catfish turning a pale ghostly white color.

This is seen most often in new fish that are added to an established aquarium. The good news is, it’s not usually fatal and if you take the proper precautions, your fish will likely recover just fine.

It’s simply a stress response to being moved into a new aquarium and new environment. Most people don’t think about it, but buying fish is actually quite stressful for them.

Your Cory was probably just fine at the store, but once you take him home and plop him into a new tank with different water parameters, that’s when things start to go downhill.

The new fish is confused, doesn’t know where he is or what to do. All he knows for certain is a big scary net came and scooped him away from all his friends, and dumped him into a small bag.

Then he was driven home in a car and plopped into a new tank.

This is a lot for any fish to handle and it’s no wonder they get stressed out. When fish are stressed, their immune system takes a hit and they become more susceptible to diseases. You can see this visually by the colors becoming pale and ghostly.

So if your Cory catfish turns pale after being added to a new aquarium, it’s likely due to stress and he should recover within a week or two as he gets used to his new home. Try to make it easy on him!

If he doesn’t, then there could be another underlying issue at play.

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Sick fish

If you have a corydoras that’s already been in an established tank for a while and was previously healthy, but then suddenly turns white or pale, it’s likely due to illness.

There are a number of diseases that can cause this symptom, including:

  • Bloating
  • Ich
  • Columnaris
  • Hexamita

If you notice your fish turning pale and see any other symptoms like lethargy, loss of appetite, or abnormal swimming behavior, then it’s time to take a better look at what could be causing it and dose medications accordingly.

Many of these illnesses can be treated if caught early enough, but some are fatal. So it’s always better to err on the side of caution and get your fish checked out by a professional if you’re unsure what’s wrong. Fish forums are a great place to get advice from professionals for free.

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One of the less common, but still possible reasons for a cory catfish turning white is malnutrition. This is more likely to be an issue if you’re keeping a group of corys and not all of them are affected. It could be that one fish is hogging all the food and the others are getting left behind.

A well-balanced diet is essential for all fish, but especially for corydoras who are bottom dwellers and might not get their fair share of food if there’s a lot of competition.

Make sure to feed small frequent meals throughout the day rather than one large meal. This will help ensure that all your fish are getting enough to eat.

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Other things besides new fish syndrome can cause stress in corydoras. They are sensitive fish and even small changes to their environment can be stressful.

Some things that might stress them out include:

  • Changing the water parameters too much or too quickly
  • Having an overcrowded tank
  • Not having enough hiding places
  • Poor water quality
  • Aggressive fish that are stressing out the cories

If you notice your corys turning pale and see other signs of stress like abnormal swimming behavior or loss of appetite, then take a look at their environment and see if anything has changed that could be causing it.

Corydoras are sensitive fish and even small changes to their environment can be stressful.

And not all corydoras in the same tank may display the same stress response. If there is another underlying condition that has lowered an individual’s immune system, that fish may be the first to show signs of stress.

The best way to prevent stress in corydoras is to make sure their environment is as stable as possible and to slowly acclimate them to any changes.

If you do need to make a change, like adding new fish or plants, do it gradually over the course of a week or so to give them time to adjust.

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Lighting and substrate color

Sometimes corydoras just appear to be pale but are actually perfectly fine. This can be due to the lighting in your tank or the color of the substrate.

If you have a darker colored substrate, for example, your corys might look pale in comparison. Or if the lighting in your tank is very bright, their colors might appear muted.

Matching tank colors with the color of the fish is a common issue with all fishkeeping, not just corydoras. It’s something to be aware of but usually not something to worry about unless you’re trying to show off your fish in a photo or competition.

In our opinion, corydoras colors show up best with a dark substrate and low to moderate lighting.


Owner of AquariumGravel.com and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!