Guppies Dying: What's The Cause?

why are all my guppies dying

Guppies are supposed to be a sturdy fish, but there are many reasons why they might be dying. The most common causes are poor water quality, low oxygen levels, and diseases. Guppies are very sensitive to ammonia levels, and even a tiny ammonia spike might wreak havoc in your tank. Guppies are also prone to various diseases, including fin rot, flukes, gold dust, and the White Spot disease. Another factor could be the temperature of the water, as guppies are tropical fish that prefer water temperatures between 72 and 82 degrees Fahrenheit. If the water is too cold, it can compromise their immune system, and if it's too warm, it can decrease oxygen levels. Additionally, guppies are known for their fast breeding, and baby guppies tend to have a lower survival rate as they become live food for larger fish or fall victim to health issues due to their weaker immune systems.

Characteristics Values
Water quality Poor water quality, including high ammonia levels, can cause guppies to die.
Oxygen levels Low oxygen levels can lead to guppy death.
Temperature Suboptimal water temperatures can cause guppy death.
Genetics Weakened genetics can make guppies more susceptible to death.
Stress Guppies can die from stress caused by factors such as breeding or external factors like loud noises.
Fry survival rate Guppy fry have a low survival rate due to being eaten by larger fish or having weaker immune systems.
Tank mates Aggressive or carnivorous tank mates can kill guppies.
Diseases Guppies are prone to diseases such as fin rot, flukes, and the White Spot disease.
Cycling issues Issues with aquarium cycling, such as ammonia spikes, can lead to guppy death.
Overstocking Overstocking the aquarium can lead to poor water quality and oxygen depletion, causing guppy death.


Poor water quality

Tap water contains chlorine, which is deadly to guppies, and must be treated before adding it to your aquarium. You should also test your tank water for ammonia, nitrite, and nitrate levels. Ideally, you should keep your tank water at 0 ppm of ammonia, 0 ppm of nitrite, and less than 40 ppm of nitrate. If you find that any of these levels are too high, you should do a 25% water change and consider using a water conditioner like Seachem Prime to detoxify the water.

Regular water changes are key to keeping your guppy fish healthy. It is recommended to change 20-30% of the water once a week and to vacuum the substrate of your tank at least once a month to remove debris, which can cause ammonia problems.

Before adding fish to your aquarium, you must cycle it first. The cycling process will take 1-2 weeks, depending on the size of your tank. You should add de-chlorinator and nitrifying bacteria, and wait for the beneficial bacteria to colonize the entire tank. Once the tank is cycled, perform a water test and add fish. Continue to monitor the tank for at least one week after adding fish.


Low oxygen levels

Guppies cannot survive without oxygen. They breathe through their gills, which pump water through their bodies and derive oxygen from it. Guppies will struggle to breathe in low-oxygen conditions, which can lead to illness and, in the worst-case scenario, death.

  • Water temperature: Warmer water contains less dissolved oxygen than colder water. Therefore, warmer water temperatures in your tank will result in lower oxygen levels. It is important to note that guppies prefer warmer water, so maintaining the right temperature is crucial.
  • Overcrowding: Guppies reproduce quickly, and their population can increase within a few months. Overcrowding can lead to lower oxygen levels, which can be fatal. To control the population, separate the fish into different tanks or introduce only male guppies.
  • Medication and chemicals: Some medications and chemicals used to treat water can decrease oxygen levels. Be cautious when using such products and compensate for any oxygen loss.
  • Lack of surface agitation: Gas exchange occurs at the water surface, so surface agitation is vital for maintaining oxygen levels. Ensure your power filter is placed slightly above the water level to facilitate proper oxygen flow.
  • Lack of aeration: Using an air pump can help increase oxygen levels by stimulating the water surface and driving oxygen into the water. It also creates an attractive look in the tank with bubbles.

To prevent low oxygen levels in your guppy tank, consider the following:

  • Regular water changes: Change about 50% of the water daily or a few times a day if your guppies are struggling to breathe.
  • Water temperature control: Maintain the water temperature within the optimal range for guppies (72-82 °F or 22-28 °C). Colder water can hold more dissolved oxygen.
  • Proper filtration: Ensure your filter is working effectively to remove waste and debris, which can contribute to oxygen depletion.
  • Aeration: Use an air pump or similar device to increase oxygen levels and create surface agitation.
  • Plant addition: Adding plants to the tank can help increase oxygen levels and provide hiding spots for guppies.
  • Population control: Avoid overcrowding by separating guppies into different tanks or introducing only male guppies to control reproduction.



Guppies are susceptible to various diseases, which can be caused by poor water quality, bad genetics, or stress.

Poor Water Quality

Guppies are vulnerable to poor water quality, which can lead to a build-up of toxins and pollution in the tank. High levels of ammonia, nitrate, and nitrite can be harmful or even fatal to guppies. Tap water also contains chlorine, which is deadly to guppies and must be treated before adding it to the aquarium.

Bad Genetics

Guppies with poor genetics may have a shorter lifespan and be more susceptible to diseases. Inbreeding can result in weaker generations of guppies that struggle to survive in changing environments.


Stress is a leading cause of guppy death. Transportation, aggressive tank mates, and the spawning season can all induce long-term stress, weakening their immune system and making them more prone to diseases.

Common Guppy Diseases

Some common diseases that affect guppies include:

  • Ich (white spots on the body)
  • Velvet (gold dust on the body)
  • Fin rot
  • Flukes
  • Tuberculosis

Preventing and Treating Diseases

To prevent diseases, it is important to maintain good water quality, provide a stress-free environment, and quarantine new fish or plants before adding them to the main tank. Early treatment is crucial, and sick guppies should be isolated and treated promptly.

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Water temperature issues

Guppies are tropical fish and require warm water to survive. They can survive in water temperatures as low as 60°F (16°C) but are not meant to live in cold water. The optimal temperature range for guppy water is 74°F to 82°F (23°C-28°C). Guppies can survive for more than 48 hours in water below the optimal temperature range of 72°F-82°F (22°C-28°C), but they will be at risk of hypothermia.

If the water temperature drops below 74°F (23°C), you need to take action to prevent your guppies from getting sick. Guppies can withstand water temperatures as high as 90°F (32°C) briefly, but if the water temperature rises above 82°F (28°C), you must act to prevent your guppies from suffocating. Warmer water has lower oxygen levels, and if the temperature is too high, there may not be enough oxygen to sustain life in the aquarium. This can cause your guppies to suffocate.

Guppies are highly susceptible to temperature changes, and constant fluctuations can make them sick. Therefore, it is important to keep the water temperature stable. To do this, ensure your aquarium is large, keep it away from drafts and direct sunlight, and use a water heater.

If you are keeping baby guppies, or fry, in a nursery aquarium, the ideal temperature is higher than for adults: 26°C-27°C (78.8°F-80.6°F).


Ammonia, nitrite and nitrate spikes

Ammonia, nitrite, and nitrate spikes are common issues in fish tanks, especially those that are new or improperly maintained. These spikes can be deadly for guppies, so it's important to understand their causes and how to address them.

Ammonia is produced by the breakdown of waste in the tank, including uneaten food and fish waste. High ammonia levels can lead to instant death or ammonia burns, which are also fatal. To prevent ammonia spikes, avoid overfeeding, regularly clean the filter and substrate, and perform water changes.

Nitrites are produced when bacteria break down ammonia. While nitrites are less toxic than ammonia, they are still harmful to guppies and can lead to nitrite poisoning, causing fish to suffocate. To prevent nitrite spikes, ensure your tank is properly cycled and maintain a healthy population of beneficial bacteria.

Nitrates are the final product of the nitrogen cycle and are relatively less harmful to fish. However, high nitrate levels can still be stressful for guppies and may indicate poor water quality. Regular water changes and proper tank maintenance are key to controlling nitrate levels.

  • Use a water conditioner like Seachem Prime to neutralize ammonia and nitrites.
  • Add cycled filters from an established tank to introduce beneficial bacteria and help process nitrites.
  • Perform regular water changes to dilute nitrite levels and remove waste.
  • Avoid overfeeding to reduce waste and uneaten food, which can contribute to ammonia spikes.
  • Maintain a clean filter and substrate to prevent the buildup of waste and debris, which can lead to ammonia spikes.
  • Quarantine new fish before adding them to the tank to prevent the spread of diseases and parasites.
  • Test water parameters regularly to catch any imbalances early and take corrective actions.
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Frequently asked questions

Guppies are sensitive to their environment and can die for a variety of reasons. Here are some of the most common causes:

Guppies are susceptible to poor water quality, including high levels of ammonia, nitrite, and nitrate. Tap water also contains chlorine, which is harmful to guppies. Regular water changes and testing can help maintain water quality.

Guppies prefer water temperatures between 72-82 °F (22-28 °C). Deviations from this range can compromise their immune system and lead to illness.

Guppies need oxygenated water to survive. Overstocking, poor water quality, and high water temperatures can decrease oxygen levels, causing guppies to gasp for air at the surface.

Guppies are prone to various diseases and parasites, such as fin rot, flukes, and white spot disease. Poor water quality, introducing new fish or plants, and feeding live foods can introduce diseases.

Guppies can be stressed by factors such as male aggression, overstocking, and external disturbances like loud noises. Stress can weaken their immune system and lead to illness.

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