How to Sterilize and Clean a Fish Tank After Fish Died

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by Jason Matthews



If you are the type of person who keeps fish as pets, it can be a painful experience to wake up or get back home to see the lifeless body of your fish floating in the fish tank. The life expectancy of a fish is not too high, so it is common to lose fish. When that happens, besides mourning for your favorite fish, you should also know how to clean and sterilize the fish tank so that the remaining fish are healthy.

Cleaning the fish tank after a fish dies involves more than just changing the water. You also need to clean the tank and decoration thoroughly. After that, the tank should be sterilized using vinegar and bleach solutions. 

Here, you will find the process to clean and sterilize the fish tank after a fish dies that you can use. It is simpler than you think. 

How to Clean a Fish Tank After a Fish Dies

Most fish owners often change the water after a fish dies, believing that whatever killed the fish may also affect the remaining fish. While there is no scientific premise to this belief, it is a good idea to clean the tank so that you can ensure that the remaining fish are healthy and well.

Here are the steps you can follow:

Step 1: Remove the Dead Fish

When you notice that one of the fish is dead, it is advisable to remove it right away. That way, the dead fish will not pollute the water. Some people believe leaving the dead fish in the tank is fine as it will decay and produce nutrients, and the filter will clean the rest of the waste. However, this is a risk you do not want to take. 

Step 2: Check the Filtration System

When the fish dies, the disease or parasites it had will no longer stay on the fish. Instead, they will begin circulating in the water. Hence, ensure that the filtration system is working optimally so that it can clean the water and get rid of waste. Make sure the filter is clean to effectively work to maintain a healthy living environment for the other fish. 

Step 3: Test the Water

When a fish dies in a fish tank, it can produce ammonia and other harmful toxins in the water. So, you want to make sure that you test the water to find out if there is anything wrong with it. If yes, you can find the solutions to rectify the problem. Testing is the need of the hour if a fish dies from a disease.

This will allow you to find the right treatment for the remaining fish, so they do not meet the same fate. If the fish did not die due to disease, testing will help you see if there is a spike in harmful toxins in the water. 

Step 4: Change the Fish Tank Water

Whether a fish dies due to a disease or not, it is advisable to change the entire water of the fish tank. If that is the case, remember that you will need a standby fish tank and a filtration system to transfer the remaining fish. A major water change means you will have to wait for around seven to 14 days before returning the fish to the water.

Run the fish tank with the filtration system for this period. This will kill the parasites and other disease-causing organisms, and you will have no reason to worry when you transfer the fish back into the tank. 

These steps will help you clean the fish tank and ensure there are no disease-carrying organisms and contaminants after a fish dies. However, if you want to be more thorough, you must also sterilize the tank. 

Related: How to Get Rid of Detritus Worms in Aquariums

Steps to Sterilize the Fish Tank After a Fish Dies

How to Sterilize and Clean a Fish Tank After Fish Died

The sterilization process should be done after emptying the fish tank and changing the water. Usually, you have to sterilize the tank if the fish died due to a disease or if you suspect that the death was because of a disease. 

Here are the steps you should follow to help sterilize your fish tank. 

1. Empty the Fish Tank

Discard the water from the tank and then transfer the decorations, gravel, and other hardscapes to a clean plastic tub. You will have to sterilize the items from the fish tank before you can put them back into the fish tank. 

2. Clean the Fish Tank with a Disinfectant

Rather than using a chemical to disinfect the fish tank, create your own. Mix one part vinegar with 10 parts water to make a disinfectant. Use this to wipe the inside of your fish tank. Vinegar solution is a wonderful way to disinfect and get rid of the algae and fungi growing on the walls of the tank. Don’t forget to clean the corners of the fish tank with vinegar. 

3. Use Bleach to Sterilize the Fish Tank

After cleaning with a vinegar solution, mix one-part bleach with 20 parts of water. Use this solution to rinse out the insides of the fish tank. The bleach solution will remove the harmful bacteria in the fish tank after a fish dies. It gets rid of anything that the vinegar solution can’t. 

4. Rinse the Fish Tank Well

Use clean water to rinse the fish tank thoroughly. That will remove all traces of vinegar and bleach solutions. Be generous with the water as you do not want any residues of bleach or vinegar in your tank before you fill it with fresh water. 

5. Sterilize the Hardscape 

You can sterilize the fish tank’s decorations, gravel, and other hardscapes by soaking them in the bleach solution you made earlier. Allow the items to stay in the solution for at least 15 minutes. After that, thoroughly rinse the items before putting them back in the fish tank. 

6. Change the Filter Media

Before you fill the fish tank and run the filtration system, make sure you change the filter media. The old media will harbor parasites and other contaminants from the dead fish. If you reuse it after the trouble of sterilizing the fish tank, the contaminants will be reintroduced into the tank. 

After sterilizing the tank, you can go back to step 4 of cleaning the tank, wherein you fill the tank with water and run the fish tank with the filtration system for around two weeks. You can put back the remaining fish in the tank after two weeks. Make sure you acclimate the fish to the new environment after changing the water, so they do not go into shock. 

In Conclusion

Use the steps highlighted here to clean and sterilize your fish tank after a fish dies. Cleaning is important as the contaminants from the dead fish will deplete oxygen levels in the water, which could be fatal for the other fish. When you clean and sterilize the fish tank after a fish dies, you create a healthy environment for the remaining fish. 

Related: How to Quarantine Aquarium Plants


Jason Matthews

My name is Jason Matthews, and welcome to my website. When other kids were bragging about how their dog could sit and roll over, I was bragging about my latest Betta Fish and the cool sea castle I just added to his aquarium. 

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