As you know, guppies are a widespread tropical freshwater fish type. They are attractive, vibrant creatures. Guppies can live for three to five years on average. However, many have had their guppies die unexpectedly. ‘Why my guppies are dying?’ they enquire.

Guppies die due to stress, poor water quality and diseases. Genetically weaker guppies also can die suddenly.

1. Stress: Why My Guppies Are Dying?

You might be surprised to hear that stress is the leading cause of guppy’s death—when they are stressed, their respiration, heart rate and blood pressure all rise. Long-term stress is one of the leading causes of poor immunity. Poor immunity is not good for fish; pathogens make them sick frequently. What causes them to be stressed? Several factors make fish stressed.


Some people had their fish die soon after placing them in their aquarium. For fish, transportation can be a nightmare at times. Tropical fish may travel long distances, sometimes by plane. They’re exhausted and scared of loud noises and physical hazards.

You purchase them after they have settled into the pet shop. They travel again to a different environment and meet different water quality parameters. Sometimes it can be too much for some guppies. They get confused and scared; incidents become vast when you are a newbie.

Transport must do with caution and as smoothly as possible.

Aggressive neighbors

Guppies get stressed by aggressive neighbors (guramis, bettas, large fish). They can be damaged or injured by aggressive fish. Keep a close eye on the neighbors. (platies, mollies, tetras, catfish, and plecos are peaceful with guppies) That is unless it is a deathly fact. However, providing hiding spaces is a viable option.

Breeding (while chasing)

Male guppies chase the females during their spawning season. Chasing causes increased stress on female guppies. Unless the female can die, make sure to put the correct male-to-female ratio.

2. Water Quality Variations: Why My Guppies Are Dying?

My guppies are dying due to poor water quality. Even though guppies are hardy fish, they should have well-maintained water quality.

The temperature of  the water

Guppies are tropical fish that require a constant water temperature. They can withstand a temperature range of 23 to 27 degrees. As they dislike being in extremely cold or hot water, they become anxious and ill. A sudden temperature change can be fatal to your guppies. (Within some hours)

An aquarium heater is essential for guppies to regulate the water temperature. Before putting any fish in the water, make sure it’s warm enough.
Inspect the heater for proper operation and take a water temperature reading. Check the water temperature regularly after adding the fish.

Make sure that the heater you purchase is the correct size. Place the heater in a precise location to ensure even heat distribution. Towards this page, you may learn further about aquarium heater placement.

pH level.

Guppies can live in a pH range of 6.9 to 7.8. They are, however, favored in alkaline rather than acidic environments. Keep them at a pH of 7 or higher to ensure their safety. First, make a note of the pH of your water supply. If there’s an error in pH, fix it. You can use water conditioners or crushed corals.

Ammonia, Nitrate and Nitrite

Fish get harmed by ammonia. It has an impact on a variety of physiological systems, including neurons. Ammonia can throw fish into a coma or perhaps kill them. In a healthy aquarium, ammonia levels should be 0 ppm.

Ammonia is generated during the digestion of fish waste, as you may know. Ammonia is converted to nitrate by beneficial bacteria. As nitrate is also hazardous to fish, it should keep nitrate to a minimum in a healthy aquarium. However, beneficial bacteria convert nitrate to nitrite, which is less poisonous.

Measure and record nitrogenous components on a regular schedule. Cycle your fish tank correctly before adding guppies.

How to cycle a fish tank in 24 hours?

Chlorine and chloramine

In tap water, chlorine and chloramine are present. Some newbies put their newly purchased fish in untreated tap water. Chlorine and its components are deathly toxic to fish. Use a de-chlorinator to get rid of it.

3. Weaker Genes

You may have seen some stunningly attractive guppies in aquariums, but they are not seen in the wild. Who are they, exactly? They’re inbred guppies. When breeders discover significant factors in a guppy fish, they continuously try to create these valuable guppies. They do this by mating closely related guppies repeatedly (Inbreeding).

Even if they are attractive, inbred generations are weaker than usual. They have a limited growth rate and fecundity and can’t survive in changing environments.

Wrapping Up

Guppies are hardy fish, but they die due to unclear reasons—a few possible reasons for the sudden death of guppies. First is stress; due to traveling, fighting neighbors or spawning seasons. Poor water quality is another deathly fact for guppies. With that, genetically weak guppies might die without any showing reasons. 

Read out.. Find out..
* Guppy Fish Care Guide
* Guppy Fish Breeding Guide 2023
* Complete care Guide For Platy Fish

I am Bruce Daniel Holgate from Los Angeles, the founder of, environmental scientist and content writer. Researcher and hobbyist in aquarium keeping and fish breeding with 20 years of experience. I'm willing to share my knowledge with you all.


  1. Hello,
    I had a question about my guppies. I have four adolescent male guppies, and today I cleaned out their tank for the first time since I bought them 8 days ago. Before I changed the water they were all happy and thriving. While I was cleaning the tank, I had all four of them in a different container with the same water. I finished cleaning the tank and put the conditioner into the water and let the filter run for a few hours, because I got a new one and wanted to make sure it functioned properly before putting the fish in. When I went to put the fish back in the tank, I noticed the biggest of the four was laying on it’s side in a corner. The other three fish are about the same size but the biggest is much larger than the rest. He is not fully grown though. He was having a lot of trouble swimming, because he seemed to be moving his two front fins, but not his tail at all. He was unable to remain balanced and was floating around sideways and upside down, but his gills and two front fins were still moving in a way that looked like he was attempting to swim. I put the three healthy fish back into the tank (they are all still fine) and kept the struggling fish in the separate container with the original tank water. About 30 minutes later, I found him without his gills or fins moving, very clearly dead. I am going to take his body back to the store where I bought him with some water to be tested, but do you think that my other fish are in danger or that they possibly hurt him? Thank you so much for your advice.

    • Hello Anna, Can you provide me with a few additional details on your matter? 1. Are you 100% sure the large guppy fish is healthy before you remove it? 2. Did you cycle the tank before adding fish eight days ago?

  2. Pingback: Everything You Need to Know about Guppy Fish Breeding – Aquarium Bee

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