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can corydoras change colour?

Can Corydoras Change Colour?

Corydoras are not usually known as being the most colourful fish around, but if you are a fish parent to some corydoras, you might have noticed that they have changed colour. Is this normal or is it something to worry about?

Corydoras can change their colour and markings due to age, breeding status, and stresses caused by their environment such as temperature, diet, water quality, over-crowding, bullying, and diseases.

In this article, I’m going to share with you the possible reasons why your corydoras can change colours, when they first get their colour, and how you can help to make them more colourful.

So without further ado let’s dive in!

do corydoras change colour?
Arched Corydoras.

Here are some possible reasons why your corydoras is changing colour:


When you look at the fish in the pet shop or online, you will have noticed that some of them are brighter in colour than others, or have more prominent markings.

But when you bring them home and add them in the tank then you might notice that your brand new corydoras has started to change their colour. They can become noticeably paler.

So why does it happen? It is due to their sudden change in environment.

Colour changes, discolouration or spots on your fish are some of the signs that indicate they could be suffering from stress.

Now, this stress could be due to many reasons. So let’s also discuss them one by one.

1. Sudden Change In Environment.

A sudden change in environment can cause the fish to feel stressed or frightened, as they are unsure of their new surroundings. You will notice that any new fish added to your tank will look pale in colour. As they get used to their new home you will see their colouring gradually getting brighter.

striped corydoras
Striped Corydoras.

2. Under or Over Populated Tank.

Whenever you put too many fish in the same tank then the chances of stress between the fish increases dramatically.

The same can be said for there not being enough fish in your tank.

Corydoras are fine on their own, but they are happier when they have at least one friend to hang out with, so if possible, try and keep them in at least a pair.

If you have a big enough tank that can accommodate more than 2 comfortably, I would get more than 2, as it will bring out their personalities.

3. Incorrect Temperature.

Most breeds of corydoras require between 68-79 °F (20-26 °C) water temperature.

Keeping your corydoras in too hot or too cold water can cause them to feel stressed which will ultimately affect their colour. It is also bad for their health. Make sure you check the correct temperature of the species of corydoras you have, or want to buy, as different species have different requirements. Some species prefer their water temperature at the cooler end of the scale, while others prefer warmer water.

4. Aggressive Tank Mates.

If you have aggressive tank mates that like to bully your corydoras, then they are going to start to feel stressed. Corydoras are really peaceful, and just like to mostly mooch about the bottom of the tank.

You should have some ornaments as hiding places in your tank. as well as some plants. This will reduce the chance of the fish coming too close to each other and trouble brewing.

Also, tankmates should always be chosen wisely so that they don’t stress the fish you already have in your tank.

5. Poor Water Quality.

Not having good water quality in the tank will not only impact the colour of your corydoras but also it will cause it to get stressed. Make sure you test your water regularly, and carry out partial water changes when required.

pygmy corydoras
Pygmy Corydoras.

What is Stress in an Animal?

Stress is whenever an animal is not able to maintain its normal physiological state because of various factors that is affecting its well being.

Stress is caused in a fish whenever it gets in a situation which is outside its level tolerance. Some fish species have a higher level of tolerance than others.

It is your responsibility, as a fishy parent, to make sure that your fish don’t get stressed and thus remain healthy, active and retain its bright colours.

There are other reasons why you may see a change of colour in your corydoras, which I will delve into below:


Getting older can be a factor leading to a colour change in your corydoras. And this is not just with fish. In any living body, as it starts aging, the body’s systems and functions start to deteriorate slowly.

With fish though, it can be as simple as going from a baby to an adult fish, especially with the males.

With ageing, cellular growth is reduced. So if your fish is getting on a bit, you may start to notice a change in their colour.

One side note: If your corydoras is lying on the bottom of the tank and has been for some time, and is looking very pale (almost translucent), there is a very good chance they are dead, or close to death. Hopefully, you will have noticed a change in their colour well before this, and have taken steps to rectify any problem.

Related Post:

What to do when your Tropical Fish Dies

Change In Water Parameters

The water parameters also impact the change in the colour of a corydoras. If you haven’t maintained your tank for sometime, then surely the level of toxins might have increased.

According to, differences in the mineral content of the water where a fish was born and where it is living now can also cause the change in the colour of a fish.

So bad water conditions, or a big difference in pH levels can be a few of the reasons why your corydoras has changed colour.


You might be noticing colour change in your corydoras because of infection or disease.

For example, if your fish is suffering from Ick, then you would notice small white spots on their skin and fin.

Improper Diet.

Although not directly, food plays a vital role in the colour of your corydoras.

The quality of diet you give to your fish and also the amount will decide whether they will show bright colours or dull colours.

If you give good quality food to your fish they will become healthier – so your fish will show brighter colours.

If you give bad quality food that lacks nutrients – your fish could become ill and weak, and will start showing dull colours.

As a general rule, you shouldn’t overfeed or underfeed your fish. And regarding the quality of the food, the more nutrients you give to them, the better it is for them.

I wrote an article about whether fish can eat human food, which you can have a read of here.

When Do Corydoras Get Their Colours and Markings?

bandit corydoras
Bandit Corydoras.

Before knowing how to help enhance the colours of your corydoras, it is important to understand when they start gaining colours.

Firstly, it is important to factor in that most corydoras follow a colour scheme of some sort of variation between black, white, brown and grey, They are never going to be massively colourful like some other species of tropical fish are.

Corydoras are more known for their markings. Some have stripes, some have spots, and some have a mixture of both.

At first, baby corydoras may not look vibrant. But when they get to between 1 to 6 weeks, they start to gain their lovely patterns and markings.

Genetics, diet and metabolism are some of the factors that contribute to when your corydoras will get their markings.

Male Corydoras tend to have much more prominent markings than females simply because during mating this help them to attract the mates. They need to stand out from the crowd!

How Can I Make My Corydoras Look its Best?

Here are some tips to make your corydoras stand out in your tank:

  1. Make sure your corydoras are fed adequately. Getting the proper amount of food is crucial for growth and colouration.
  2. Always try to give quality food to your corydoras which is full of nutrients. This will help ensure better growth and colouration.
  3. Make sure to keep your corydoras with peaceful tank mates that don’t harass or bully them.
  4. Have them in an adequately sized tank, and also avoid overcrowding.
  5. Maintain proper and required water temperature and water quality for your corydoras. This will allow them to remain active, healthy and show off their lovely markings.
  6. Make sure you have the correct male to female corydoras ratio. Ideally, it should be 1 male to 2 females, although they will be fine with one of each as well.
  7. Have enough hiding places, use proper lighting and create such an environment to keep your fish stress free.

Why Has My Corydoras Turned Black?

Now, this can be harder to spot with corydoras due to many of them having black markings anyway, but this is something you need to try and keep an eye open for.

Generally, corydoras can start to turn unusually black due to infection, stress or due to ammonia positioning.

If you are noticing the tail of your corydoras turning black, and it has appeared fairly recently, then that can be because of some form of infection.

High ammonia concentration is not good for fish. Their tissues can get damaged and even cause change in coloration, or black patches could appear.

Why is my Corydoras’ Head Turning Red?

Generally, due to ammonia poisoning, red spots can appear on your corydoras. Ammonia poisoning occurs when the fish tank’s pH level gets elevated.

If there is a problem with your ammonia levels, you may notice your fish gasping at the surface for air. You may also see that the gills of your fish become a reddish colour.

Make sure you carry out a full water test.

Ammonia poisoning is more likely to occur because you have either added fish to a tank that hasn’t fully cycled yet, or you have added too many fish to the tank too quickly, which has caused the ammonia to spike.

If you add any fish to a new tank then the ammonia level may rise quickly simply because of the lack of the beneficial bacteria which can transform these into nitrates.

Ammonia, even in small amounts can be quite harmful for your fish. And it is always better to avoid ammonia poisoning rather than having to treat your fish for it.

corydoras changing colour
Group shot!


Can corydoras change colours? Yes, to an extent. Any change of colour in a corydoras will tend to be quite subtle due to their muted colourings in the first place. If they do start to change colour, or start to look paler, it will mainly be because of stress or some change in their environment. But there could also be reasons like aging, poor water quality, insufficient diet, and infection that can cause a change in colour.

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