Why Do Guppies Change Color? (Reasons + What To Do?)

Why Do Guppies Change Color? (Reasons + What To Do?)

Image of a guppy losing its color

Guppies change their color due to poor water quality, infections, bullying, and inappropriate nutrition. Female guppies may also become pale when pregnant. Besides, the colors of guppies brighten when they are trying to attract a mate, while they lose their colors when they are ill or stressed.

Let’s talk about this in detail now.

How Does A Guppy Get Its Color?

An aquarium with guppies is a colorful sight. But did you know that guppies are not born with these beautiful colors?

Guppy fry are plain and grey. They get their colors a few weeks after they are born.

Factors such as their genetic makeup, quality of nutrition, and tank conditions determine when guppies get their colors.

On average, guppies get their colors between four to six weeks of age.

Another interesting fact is that male guppies are more colorful than females.

Due to chromosomal differences, male guppies have more attractive colors and designs compared to female guppies.

Interestingly, these bright colors are also nature’s way of helping male guppies find their mates.

In the guppy world, bright colors indicate good health.

Females prefer brightly colored flashy males over those with dull colors.

So, flashy male guppies use their beautiful colors to attract partners.

Once guppies get their colors, they usually don’t lose their colors.

Color loss in guppies generally indicates that something is wrong with the fish or its surroundings.

Hence, you should look for possible causes and fix the problem before it gets out of control.

Reasons Guppies Change Their Colors

The following reasons can cause guppies to change their colors.


Guppies are hardy, adaptable fish. Although they adjust to unfavorable conditions, they are not immune to stress.

Unfavorable tank conditions, incompatible tank mates, poor water quality, or external noises stress them out.

Guppies are very sensitive to water quality.

So, poor filtration or sudden changes in the water chemistry can cause them stress.

As a result, they may lose their bright colors.

Similarly, guppies need plenty of space to swim. Keeping them in a small or overcrowded tank can adversely affect their well-being.

Guppies will also lose their colors due to stress if their tank mates bully them.

Poor nutritional quality will also make them appear pale and colorless.


Guppies are prone to various parasitic infections. Some diseases like ich, fungal skin diseases, and fin rot will affect their coloring.

Other diseases may not directly impact their color. However, they can cause stress.

A stressed guppy will not be as bright as a healthy one.

Some of the diseases that commonly affect guppies include swim bladder disorders and dropsy.

In most of these cases, guppies will regain their original colors once they recover from their illness.

Improper nutrition.

Nutrition plays a significant role in deciding the colors of guppies.

Although guppies will eat anything, not all food is equally good.

They thrive on a rich and varied diet that offers balanced nutrition.

If you can replicate their diet in the wild, it will be the best thing for your guppy fish.

You can sustain your guppies on store-bought fish pellets or fish flakes.

However, if you don’t feed them enough or if the quality of their food is inferior, their colors will get affected.

Occasional treats and suitable supplements will help your guppies look brighter and grow to their maximum potential.

Water quality issues.

Guppies don’t do well in poorly maintained aquariums.

They are very sensitive to ammonia spikes, pH variations, temperature fluctuations, and toxin levels.

When exposed to chlorine, heavy metals, or sudden changes in the water chemistry, they become ill.

High ammonia or nitrite levels can also poison your guppies.

All these conditions will adversely affect their bright colors and make them appear dull.


It is normal for guppies to look pale or slightly discolored at night.

Guppies are diurnal creatures like us. They are active during the day and rest at night.

When they sleep, they tend to become motionless and float.

When you switch off the tank lights at night, their bright colors will also seem to fade.

However, it is not a cause for concern. Guppies will regain their colors in the morning or when the lights are switched on again.

What To Do If Your Guppies Change Color?

Unless your guppy is sleeping, it should not lose color.

So, if your fish appears dull or discolored, it is best to investigate the cause of it.

The first step is to check for illnesses. Look for physical signs of infections like discoloration or the appearance of spots.

You can also look for any changes in feeding and behavior.

You may have to quarantine your fish if it has an infectious disease.

Treat it with suitable medication, and its colors should return as you nurse it back to health.

If loss of color is not linked to illness, look for water quality issues.

The tank filter should be working at optimal capacity. You should also check if the water pH and temperature are correct.

Use a testing kit to check the toxins in your tank. Eliminate any trace of chlorine or chloramine.

Also, check for the alkalinity of the water and maintain it within optimal limits.

When you restore the proper water parameters, your guppy should regain its colors.

If none of the above causes seem to be present, check for stressors. Is your guppy being bullied?

If so, it is a good idea to offer more hiding spaces or separate it from aggressive tank mates.

Also, pay attention to the quality of food and lighting conditions in the tank.

Do Guppies Change Color When Pregnant?

Female guppies are not as colorful as males. Nonetheless, you can use their colors to identify if they are fine or not.

The color of female guppies may fade when they are pregnant.

This discoloration will most likely be accompanied by a change in their shape and behavior.

The stomach of pregnant guppies will look swollen, and the fish will take on a boxy shape.

Pregnant guppies have a visible and prominent gravid spot. As the pregnancy progresses, the gravid spot becomes darker and blacker.

Since a guppy’s gestation period is less than a month, these changes will be in quick succession.

So, you can easily identify these changes and link the color change to pregnancy.

Once the female guppy drops the fry, she will slowly regain her normal color.

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