My Guppy Died After A Water Change. (Reasons+Prevention).

We, as aquarists, face several issues at the beginning of our fish keeping journey. One of them is fish dying after a water change. So, my guppy died after a water change. Why? Let us find out.

A major water change after a long gap causes your guppy to pass away because of stress. Keep the water parameter the same as a quick change in water parameters will cause issues. Never clean the biofilter media from tap water as it will eliminate the good bacteria from the tank.

This article will discuss the stages of performing a water change and the possible reason behind the guppy dying after a water change. So let us get into it.

Does water change make guppy pass away?

Water change is essential to keep the aquarium clean.

Performing a massive water change can lead to guppy coming under stress and passing away.

If you have not done a regular water change for weeks or a year and suddenly perform a major water change one day, this can be an issue.

Your guppy will adapt to the water condition throughout this year and will be familiar with that, and if you suddenly change the water after a long time, they will come into stress and can pass away.

With water conditions, the water parameter is the next thing to be considered when doing a massive water change after a long time.

If there is a major difference between the water parameters of aquarium water and fresh water, this can make your guppy come under stress.

There are ways to do a water change to prevent your guppy from coming under stress and various other problems, which we will discuss in this article.

Reasons behind guppy passing away after a water change?

There can be various possible reasons behind guppy passing away after a water change:

  1. Doing a massive water change after a long time.
  2. Change in water parameters while performing a water change.
  3. Elimination of good bacteria from the filter. 

Regularity is the main factor behind guppy passing away or coming under stress when doing a water change.

If you are not performing a regular water change and then suddenly doing a massive change one day, it can result in your guppy passing away.

The second main factor is the change in water parameters when doing a water change.

When you do a massive water change like 50-70%, water parameters change.

Because of the change in water parameters quickly, your guppy will come under stress and even pass away.

The third main factor is eliminating good bacteria by cleaning the filter and filter media.

If you clean the aquarium filter when doing a water change, then the good bacteria present in the filter get eliminated, resulting in a spike of ammonia, causing the passing away of your guppy.

Should we perform the water change?

A regular water change is essential for your guppy health.

Water change cleans your guppy aquarium.

With time your guppies aquarium will get dirty from the leftover waste by guppies and other debris.

Filter helps you clean your aquarium, but water change will help you avoid the risk of an ammonia spike.

You cannot see the water dirtiness of your guppies aquarium with your naked eye.

Whenever we provide our guppies food, they don’t eat them all, and some of the leftovers get into the bottom of the tank.

These leftovers decompose at the bottom of the tank and make the substrate dirty and water polluted over time.

Also, the food your guppy eats gets released in the water as urine and poop.

And over time, the waste increases as chemicals such as nitrate and the solid debris in the gravel.

Not doing water change will slowly eliminate the trace minerals and elements from the water.

Trace minerals and elements are essential for keeping the water chemistry and your fish stable.

Lack of trace minerals will affect the hardiness and health of your guppies.

It will also affect the biofilter media we use to eliminate ammonia spikes from the water.

A water change will not cause any issue to your guppies if you take care of these things:

  1. Changing the water regularly then doing it in a long gap.
  2. Taking care of water parameters while changing the water.
  3. Ensure that you don’t eliminate the good bacteria from the water filter and filter media.

How to perform water change?

Quantity of water we should change:

  1. Change 10% of water if you have a small tank.
  2. Change 20-25% of water if you have a large tank.
  3. Change 10-15% of water if you have a large tank with fewer fish.

Things to take care of while doing a water change:

  1. Never perform a massive water change unless recommended because of some issues.
  2. Never wash the biofilter media with tap water, as washing it will eliminate all good bacteria.
  3. Ensure to provide your guppy the same or close to water parameter after a water change. 
  4. When you refill your guppies aquarium with water, then make sure not to add the water at super speed as it can disturb the substrate, and the water can get dirty. 

Things needed while performing a water change:

  1. A sponge 
  2. A gravel siphon
  3. Two plastic bucket

Steps to perform water change:

  1. You have to pretreat the bucket of tap water to clean it.
  2. Unplug the equipment like heater, aquarium light.
  3. Clean the filter, making sure not to clean the biofilter media from the tap water. Instead, you can clean the biofilter media from the tank water. 
  4. If any artificial decor is dirty, you can take them out and clean them.
  5. Now, start cleaning the tank’s walls with the help of a sponge.
  6.  Siphon out if any solid debris is present in the gravel with the help of a gravel siphon.
  7. Now, suck the water out from the aquarium with the help of a gravel siphon.
  8. With the help of a thermometer, note the temperature of the water remaining in the aquarium.
  9. Refill your guppies aquarium with the bucket of water you have pretreated, matching the water temperature of the tank water.
  10. If the water temperature doesn’t match, then wait for some time until it matches.You can use a heater to match the water parameter if needed.  
  11. Reconnect the filter and the heater back to the aquarium. 

Doing a regular water change is essential.

By applying the correct method of changing the water, your guppy will not come under stress.

If you have not done the water change for a long time, go for a small water change first.

Start by changing less than 5% of the water and slowly increasing the percentage over time.

Take care that the good bacteria are not eliminated while doing a water change. The water parameter is the same as the remaining water in the tank and the clean pretreated water you will add.

Keeping care of these things will not make your guppy come under stress and pass away.


Doing a massive water change after a long time without any water change can make your guppy come under stress and pass away.

If not done a water change for a long time, start doing 5% of water change and increase the percentage over time.

There are things to be taken care of while performing a water change, like not cleaning the biofilter media with tap water, matching the water parameter of water you will add, and more.

Regular water change is essential to keep your aquarium water clean and safe from various infections and diseases.

Reference: ResearchGate


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