Main Reasons Why Guppies Die

Image of guppies swimming in tank

Given below are the main reasons that result in the untimely death of guppies:

  • Poor water quality,
  • Stress,
  • Uncycled tank,
  • Overfeeding,
  • Overcrowding,
  • Illness,
  • Unsuitable water temperature,
  • Incompatible tank mates,
  • Irregular tank maintenance,
  • Unsuitable living conditions,
  • Poor gene inheritance, and
  • Increased ammonia levels.

Let’s now discuss each of these reasons one-by-one.

Poor Water Quality

This is the most common reason for guppies to die.

If your aquarium’s water quality is poor, then your guppies will pay the price for it.

Water gets polluted rapidly due to the waste excreted by your guppies, uneaten guppy food that decomposes, and irregular water changes.

If the water in your tank is not clean, it turns toxic. Toxic water is very harmful to your guppies.

Also, contaminated water has lower oxygen levels as compared to fresh and clean water.

These all things compound and result in the death of your guppies.


Stress is another primary reason for the untimely death of your guppies. Stress kills the fish slowly.

Since your guppies cannot show emotions to express their feelings, you may fail to realize that they are stressed.

Stress occurs if the conditions in the aquarium are not suitable.

Bullying, illness, poor water quality, a sudden change in the water temperature, or simply a new environment can cause stress to your little ones.

Uncycled Tank

Setting up a tank does not merely mean putting water in the tank and adding your fish.

Your tank should be properly cycled before adding the fish.

If you place your guppies before cycling the tank, chances are high that your guppies will die.

Guppies need beneficial bacteria that will break down and remove the waste from the tank.

The process of establishing bacteria into your newly set up tank is called Cycling of the tank.

It takes at least a couple of weeks to cycle the tank.


Everyone loves to feed their little ones. But rarely do we realize that overfeeding can be fatal.

You should only feed your adult guppies once a day. Overfeeding will result in more fish waste in your tank.

Also, if you overfeed guppies, it will result in leftover food in the tank.

This will contaminate the water in the aquarium and increase the ammonia levels, which will result in health issues for your guppies.


Overcrowding is another reason for your guppies to die.

When we buy the fish, we often tend to buy too many without considering our aquarium’s size. This often turns disastrous.

If you have a small tank, overcrowding is a significant concern.

The more the number of guppies you have in a tank, the lesser will be the oxygen levels.

Also, the tank will be more contaminated as your guppies will poop. This will result in depletion of oxygen in the water.

Your guppies will suffocate due to less oxygen, resulting in the death of your guppies.

Furthermore, your guppies will get less space to swim due to overcrowding.

This will result in stress, which again will lead to the early death of your guppies.


Illness is also one of the main reasons for your guppies to die. A sick fish needs your time, attention, and proper medication.

Your guppy may have already been carrying some illness when you first bought it and introduced it in your aquarium.

Or, it may fall sick afterward.

Your guppy fish can fall ill due to poor water quality or bad genes.

The most common diseases among guppies are ick and fin rot.

Ick causes white spots on the guppy body. These diseases can be treated with proper medication.

However, if your guppy has tuberculosis disease, it is fatal and can lead to its death.

This disease can even spread to other guppies if the sick guppy is not immediately removed from the aquarium.

Unsuitable Water Temperature

Water temperature is another reason for guppies to die.

Guppies are tropical fish, and so they thrive well in warm water.

The ideal temperature for guppies is between 72°F  to 82°F (22°C to 28°C).

However, they can tolerate and survive in temperature up to 64°F (18°C).

Guppies can die if exposed to other unsuitable water temperatures.

Too much warm water also poses a threat to your guppies.

If your aquarium water temperature is above 82°F (28°C), it will result in the depletion of oxygen levels.

In such a case, your guppies can die due to suffocation, as there will be less oxygen to breathe.

Incompatible Tank Mates

Not all fish get along with each other.

Fish like Mollies, Dwarf Loaches, Neon Tetras, Platies can live with guppies in the same tank.

However, fish such as Barbs, Oscar, and African Cichlids are not compatible with your guppies.

If you have an aggressive fish along with your peaceful guppies, it will result in bullying.

Your guppies will be chased and nipped by the other territorial fish. This will result in stress and can lead to the death of your guppies.

Irregular Tank Maintenance

If the tank is not adequately maintained, it can lead to guppy death.

You need to regularly clean the substrate in the tank, wipe the glasses, and perform a regular water change.

Fresh water is essential for a healthy tank. The tank is the habitat of your guppies.

If the tank itself is not maintained, your guppies cannot survive for too long and will eventually succumb to death due to some illness.

Unsuitable Living Conditions

Guppies need suitable living conditions to thrive.

If your aquarium conditions do not suit your guppies, they will die due to stress.

For example, guppies do not like a strong current.

If you have a strong current in the tank due to a large filter, your guppies will get swept away and find it challenging to swim freely.

This will result in stress, and they may die due to it.

Poor Gene Inheritance

You should be very careful when you buy guppies. You should purchase them from reliable sources.

Your guppies may look bright when you buy them, but they may have poor genetics.

Bad genes can often lead to illness and early death of your guppies.

So, it is always advisable to purchase guppies from guppy breeders.

Their guppies seldom have poor genetics and usually live a better and healthy life.

However, you can also purchase them from a pet store sometimes.

Increased Ammonia Levels

There should not be any ammonia in the tank water. Ammonia is hazardous for the well-being of your guppies.

The ammonia problem is mainly caused by uneaten food that decomposes, dead plants, dead fish if not removed immediately, dirty substrate, and dirty filter.

If the ammonia levels in your aquarium water are high, it will result in your guppies’ instant death.

Final Thoughts

Guppies are delightful pets. As mentioned above, there are various reasons for the untimely death of your little ones.

The mortality rate of guppies increases if they face any of the problems mentioned above.

Most of the time, lack of awareness results in the death of guppies.

For every aquarist, it is a learning experience as caring for a pet is not easy.

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