Why Do Guppies Die After Water Change {Reason Why Here}

Did your guppy just die after a water change? Are you wondering why do guppies die after a water change?

Guppies can be quite fragile if not looked after carefully.

There is a process you need to follow when changing their water which I will cover below.

Why Do Guppies Die After Water Change?

Guppies can die after a water change because of poor water quality after the change, overcrowding of the aquarium makes the water dirty quickly even if you change the water frequently.

50% of the reasons why guppies die after a water change is tied to this point. Most times, overcrowding of the aquarium makes the water dirty quickly even if you change the water daily, this will lead to scarcity of oxygen in the tank.

There is no way you will change the water in this kind of system, and the mortality rate will not be recorded.

Why Do Guppies Die After Water Change

Another mistake people make is this, bad water quality does not mean only when the water is dirty, fresh-looking water can be toxic to guppies.

For instance, tap water that contains chlorine intoxicates guppies, if tap water is what you have then you need to treat the tap water first before pouring into your tank.

Another reason why they die after a water change is due to a non-cycled tank.

This should be done before the introduction of fish into the aquarium, below are the steps to follow if you want to recycle your tank but have in mind it will take seven to fourteen days before it can be successfully done.

  • Get at least ten-gallon size of tank and fill it with de-chlorinated water
  • After few hours, add nitrifying bacteria to the aquarium.
  • Be patient, check back within seven days to test the nitrate, nitrite, water quality, and ammonia rate of the aquarium. Ideally, nitrate should be 20ppm, while ammonia and nitrite should not be more than 0ppm.

High rate of ammonia is part of the reasons fish die after a water change; the level of ammonia should not be more than 0ppm if you want your guppies to be healthy.

Ammonia is unavoidable in a tank because nitrifying bacteria will produce ammonia, while ammonia should produce nitrites and nitrates.

There are other things that can lead to the production of ammonia in an aquarium. For instance, the accumulation of leftover foods in the tank produces ammonia, which kills guppies during a water change.

Ensure you also get rid of dead/decaying fish, dirty filter, or substrate from the tank. Guppies hardly survive a high rate of ammonia, but prevention is crucial if you desire healthy guppies.


Bad Guppy genetics is also an issue. Some people lose their guppies because they are not buying from a trusted store, not all big pet stores that sell guppy is worthy of patronizing. Aquaculturists should know that poor genetics is the leading cause of death in guppies.

Ask a question about the species you are buying before purchase because some species die early and should not be kept.

Not all colorful guppies have good genes. Species that have good genes and can live for at least two years are albino guppies, metal, Moscow, cobra, and grass tail guppies.


Hello, I'm Jason. I'm the guy behind HelpUsFish.com. I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.

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