How to Sanitize Fish Tank After Disease


When one of your fish gets sick, it has the potential to be detrimental to the whole aquarium. That is unless you know how to sanitize a fish tank after disease.

This is also a good thing to know for the inevitable event of the death of a fish. Learning how to disinfect a fish tank after a fish dies will help your fish in the long run too.

By properly cleaning your aquarium, you can make sure that your fish have a safe environment. In this guide, we’ll walk you through exactly how to sanitize a fish tank!

Getting the Tank Ready to Clean

The first step to this process is getting your fish tank ready for sanitization. This means you have to remove your fish for now.

For now, the easiest option is to put your fish in a separate, temporary tank. They’ll only need to be in here for as long as it takes you to clean the tank.

Next, you’ll need to remove just about everything else. After all, this is meant to be a thorough clean.

This should include any plant life or decoration in your tank like fish caves. You’ll also want to remove any equipment like an aquarium filter, fish tank heater, or aquarium chiller

When you’re left with just the substrate, you have some options. Some people are happy to just vacuum it but replacing it makes for a much more thorough clean.

Creating a Cleaning Solution

Now that you have everything deconstructed and ready to go, you need to create a cleaning solution. This should be made up of about 10 parts water to one part bleach.

Aquarium cleaning process

Make sure that you don’t add too much bleach to the solution. After all, bleach is a strong chemical.

In cleaning the main aquarium with this solution, an algae pad is a great choice. Clean the interior and exterior of the tank.

Once you’re done, thoroughly rinse the tank. Otherwise, you risk putting your fish into contact with bleach remnants which is detrimental to their health.

Tackling the Filter

If you have a particularly harmful disease in the tank, it’s best to replace it completely. This can also include replacing the chemical, biological, and mechanical media.

You might notice a downside to this step. By removing all of the biological media, you’re removing all the bacteria – including the beneficial component.

This is actually fine, though, because you have to replace all the water anyway. This means you’ll have to cycle your tank again when you’re done.

For cleaning the filter, you can use the same solution from the last step. Remember, make sure that you rinse it thoroughly to remove any traces of leftover bleach.

Caring for Accessories

Now that the primary tank and filter are clean, it’s time to tackle the accessories. In this, we’ll encompass everything from aquarium gravel to decorations, plants, and external lights.

Cleaning aquarium decorations

The main thing to do is to rinse and scrub all of these items. Again, you can use the cleaning solution you used earlier on mechanical and decorative pieces.

As we’ve covered, remember to make sure to rinse these pieces thoroughly before returning them to the tank.

Returning Everything to Tank

The next step is to put your tank back together and get ready to return your fish to it. By the time you’re at this point, all of the components of your tank should be clean and disease-free.

To start out, just add in the accessories, decorations, and any component besides the fish. You won’t want to put your fish in just yet since you replaced the water, substrate, and filter media.

Instead, you need to go through the nitrogen cycle in the tank before returning your fish. If you don’t have time to do this, though, you can purchase bacteria for instant cycling.

Once this is done, you can return your fish to their tank. Then, your tank should be ready to go.

If you want to go a step further, it can also be beneficial to add fish medicine to the water. This is something to help prevent the disease from returning.

That being said, you’ll need to know what disease affected your tank. This way, you know what kind of medicine to use on your tank to rid any last evidence of the disease.

Preventative Measures to Avoid Disease in the Future

Once you clear your tank of disease and thoroughly clean your aquarium, you might have a second question. What can you do to prevent this problem in the future?

There are actually a few preventative measures that you can take to avoid disease in the future. Here, we’ll go over a few of your best options.

Be Careful Adding New Fish

This is a big point when you want to avoid contamination. If you buy new fish for your aquarium, they could bring in disease if you aren’t careful.

The best way to handle this is to have a quarantine tank handy for new fish. This way, you can keep an eye on them for a disease before they’re introduced to your other fish.

Ideally, you should keep these fish in the quarantine tank for about two to three weeks. If there are signs of disease, treat them before introducing the fish to your main tank.

Use the Right Equipment

One major point is that you need to make sure to keep your tank maintained with the right equipment. This is especially true in considering the equipment that keeps your tank clean.

For instance, using an aquarium UV sterilizer or high-quality filter can help reduce the risk of disease.


Disease in a fish tank can spell out a dangerous situation for your fish. After all, they rely on you to help them!

Once you get them through the disease, though, you’ll want to make sure it’s not coming back. The best way to do this is to follow the steps we’ve covered here to sanitize your tank!