What’s The Best Way To Clean A Contaminated Aquarium?

Cleaning a fish tank can be a really hard job to do. Particularly because it can be a life or death situation for your fish.

But do not worry, as we have collected the information you need to know about the best way to clean a contaminated tank.

So what’s the best way to clean an aquarium? First, move your fish to a separate tank. Take out the decorations. Drain the tank. Clean the dust with a paper towel. Use bleach to sanitize the tank. Rinse the tank after about 15 minutes of applying bleach. Put the water, the decorations and the fish back into the tank.

“But how do I use the bleach?” and “How do I sanitize the decorations” is what you might be thinking.

Well, keep reading to find out!

Steps To Clean A Contaminated Aquarium

You might be cleaning your aquarium because of a disease that spread in the tank or because there was some fungus over the glass.

But worry not because this method can help you sanitize the tank for both disease and fungus, or any other type of contamination.

I have made it in steps so that it’s easier to understand and follow. Here are the steps:

Step 1:

Take out all of your fish. You can buy a fish net from a pet shop for this purpose. Pick one fish at a time and slowly move them to a separate tank. The tank does not need to be anything extra; just a simple tank for your fish to stay while you clean the main aquarium.

Step 2:

Take out all the decorations, including gravel. Also, take out the filter. You can leave the decorations that are part of the tank. We will talk about how to clean the decorations and the filter later on.

Step 3:

Now drain the tank free from the contaminated water. You can use a bucket or anything that you are comfortable with to take out the water.

Step 4:

Take a paper towel and wipe the tank to remove all the dirt or dust. Wipe until fully cleaned.

Step 5:

This step is the most important one because this step will help you get rid of the fungus or the disease. You will need a spray bottle and bleach. Remember that the bleach must not have detergent in it.

Now you will have to make a solution of bleach and water. Mix 1-part bleach with 9 parts of water in the spray bottle. For example, 1 cup bleach and 9 cups water or 8 parts water and 1-part bleach are okay too.

Step 6:

Spray the solution over the tank. Make sure to spray on any items attached to the tank. Leave the solution to do its work for about 10 to 15 minutes. This time will be taken to kill all the bacteria within the tank.

Step 7:

Rinse the tank thoroughly and make sure that the bleach is completely washed away. You can rinse the tank two times just to be on the safe side.

Step 8:

Now let the tank dry for about a day. This will break down any harmful residue left on the tank.

Step 9:

Fill the water in the tank. Add a de-chlorinator and other necessary conditioners into the water and leave it for a further one to two hours.

Step 10:

You can now put back everything including the decorations and the fish.  

How To Clean The Tank Decorations And The Water Filter

You do not need to put all the decorations, the gravel, and the water filter as it is back into the tank. Because the contamination most likely has spread to all the other things in the tank as well.

So here’s how to do it:

Cleaning decorations (and gravel):

Use the same solution of bleach to clean the decorations. Leave them for about the same time as you left the tank after spraying it. After letting the bleach do its work, you need to wash the decorations thoroughly.

Decorations can also be soaked into the bleach/water solution instead of spraying. But remember that after rinsing it with water, be sure to leave the decorations to dry for 24 hours, just like you let the tank dry.

For gravel, you can boil it in water. I recommend not to boil the decorations because there are some plastic decorations that can melt when you boil them.

Another important thing is that do not try to clean your decorations in the dishwasher as the soap might be left as a residue. Soap is toxic for fishes and can contaminate the water. So do not take this risk.

Cleaning the filter:

Cleaning the filter is also one of the most important steps while cleaning your aquarium. Use the same bleach method just like you did for the decorations described above.

You might have to change some parts from the filter to keep the water clean. Cleaning your filter will maintain the cleanliness. So remember how frequently you want to change your filter.

Here is a video to help you clean your aquarium:

Important Tips You Need To Know

If you are cleaning your aquarium because of fungus, then you need to know this:

Before putting your fish back into the tank, just leave the tank with water only for a day or two. This way, you can observe if the fungus grows back or not.

Bleach alternative:

If bleach is not available, then you can also use a vinegar solution. To make a vinegar solution, use the ratio of 1:1. Put 1-part water and 1-part vinegar into a spray bottle and mix well. Follow the same method as for the bleach solution. If you need a stronger solution, then you can put 2-parts vinegar and 1-part water.

To break down the hard water build-up on the filter, put the filter in a bucket of water/vinegar solution for a few hours. This will clean the inner mechanism of the filter as well.

Filters And Media Care

Here’s the deal:

If the cause of cleaning your tank was a disease, then you might have to replace the media, which is all mechanical, biological and chemical media inside your filter.

But the problem is that the beneficial bacteria that is needed for your fish to stay alive might also go away as you replace the media.

These beneficial bacteria are bacterial colonies living in your aquarium filter. And mostly when people are cleaning filters, they simply remove the spongy material (the beneficial bacteria) from the filter. Or they just run it under a tap to remove any dirt, which kills the beneficial bacteria.

What you can do to prevent this is to detach the part where the bacteria has grown. Wash the spongy part with warm and de-chlorinated water, which is safer for the bacteria to help them survive the cleaning process. And wash the other parts of the filter with the bleach solution with the method described above.

You can also buy some water supplements to provide the tank water with these good bacteria. Here are two videos about such type of water supplements to help you understand better:

Related Questions:

Can you get sick from cleaning a fish tank?

People, especially those with open skin scrapes could get infected by bacteria while cleaning aquariums. Affected people usually develop a skin infection at the site of open cuts. So it is preferred that you cover your hands by wearing gloves while you clean a fish tank to avoid infection.

Can fish die from dirty water?

Yes, because the fish live in the water and change happen slowly, so they adjust to it. But when a sudden, large water change occurs, it causes such a drastic shift in the properties of the water that the fish often cannot tolerate and die.

What happens if you don’t change fish tank water?

Exposure to ammonia, nitrates and nitrites can have severe effects on your fish. General signs for aquatic life with unbalanced water conditions include a decline or loss of appetite, loss of colouration, reduced energy and/or a weakened immune system.

How to keep a fish tank clean without changing the water?

You need to remember to change your filter or at least some parts of it. You can also use some water supplements to avoid changing your filter more often. Also, you need to control the excessive growth of algae in your tank to keep it clean.


You might have realized after reading this to the end that cleaning your aquarium seems like a tough job. But after following all the steps and tricks described above, you might find it not so difficult once you start doing it.

And it will seem less of a tough job after you clean your tank once or twice and get used to it. Good luck with cleaning your tank!


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