How to Disinfect a Fish Tank Safely for Healthy Fish

how to disinfect a fish tank

How to disinfect a fish tank is usually not the top priority of beginner aquarists. Only when they must sterilize the aquarium after a fish dies or after a fish disease outbreak do aquarium hobbyists look for information on disinfecting the tank.

Please, do not wait for such circumstances to happen before you start learning how to sterilize fish tank and equipment. It is an aquarist skill that will come in handy more often than you think.

So, how do you disinfect a fish tank? We offer you three proven ways.

Ways to Disinfect a Fish Tank

What to prepare


To prepare the tank for disinfection, here are what you need to prepare:

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  • Soft fish net
  • Clean container for fish
  • Empty boxes
  • A flexible tube (or a gravel cleaner)
  • Bucket
  • Clean towels


As for the disinfection process itself, the required materials will vary depending on your preferred method (i.e., vinegar or bleach). We will share these items as we go through the different steps.

Step 1: Learn when to sterilize or disinfect a fish tank.

after-a-fish-dies .

Fish tank sterilization or disinfection does not occur frequently. You only need to perform this activity in some instances, such as the following.

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    • Initial Fish Tank Setup

    Aquarists must sanitize and clean new aquarium glass or acrylic to remove contaminants, residue, and other substances that might harm fish and livestock.

    • Fish Disease Outbreaks

    Hobbyists must sterilize fish tank after fish died due to disease outbreaks in the fish tank. The death-causing organism might still linger in the aquarium and infect your other fish. Sterilizing and cleaning fish tank after disease outbreaks is necessary.

    • Fungal, Bacterial, and Parasitic Infections

    These infections are easy to miss, and they often originate from external organisms introduced into the aquarium without proper quarantining. Some telltale signs are ragged and blood-streaked fins, white tufts on the body, or signs of rot around the mouth.

    • Neglected Aquariums

    Suppose you have an aquarium that has been in storage for ages, and you want to sell or use it again. Sterilizing it will help ensure no fish will ever get sick in that tank. Aquarists must also sanitize and clean used fish tank.

    • Accidental Contamination

    Curious kids might dump chemicals into the fish tank requires immediate aquarium sterilization. So do accidental spills.


Step 2: Remove all fish tank contents


You will need a soft fish net, a clean (preferably sterilized) container for the fish, and a few boxes for the fish tank accessories.

Turn off all electrical gadgets connected to the fish tank, including filters, lights, and pumps.

Then, you should carefully scoop out the fish and other livestock, then transfer them to a clean container filled with treated water. Ensure to relocate a fish at a time, never in groups.

Remove aquatic plants, rocks, filters, driftwood, aquarium decorations, and other items from the aquarium. You need an empty tank to sterilize the aquarium.

Step 3: Prepare the aquarium for disinfection.


This step requires a flexible tube to siphon the water from the aquarium. Alternatively, you can use a gravel cleaner. Paper towels, buckets, and warm water are also necessary.

Position a bucket on the floor and dip one end of the gravel cleaner in the aquarium. Place the hose’s other end in the bucket and turn on the pump to drain the water.

Douse the fish tank with warm water and wipe all surfaces, including the sides and bottom. Use a new towel once soiled.

Step 4: Disinfect the fish tank and decorations.

[su_box title=”Method 1: Using Vinegar” box_color=”#d5eaec” title_color=”#013b56″ radius=”0″]


Most aquarists recommend vinegar to clean fish tank units, especially for preparing a newly-bought fish tank or treating mineral buildup.

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  • Sanitizing and cleaning a fish tank with vinegar starts by making a disinfectant solution comprising equal parts of water and distilled white vinegar. It should be enough to soak the fish tank and decorations.
  • Fill the aquarium with the vinegar solution and leave it for two to three hours.
  • Pour the vinegar solution into a separate container and immerse aquarium decorations and accessories to sanitize them.


The vinegar method is the most effective disinfectant without bleach worries.


[su_box title=”Method 2: Using Bleach” box_color=”#d5eaec” title_color=”#013b56″ radius=”0″]


The best way to sterilize aquariums after a disease outbreak is to put bleach in a fish tank to guarantee complete disinfection. However, as it’s quite strong, pay attention to the bleach to water ratio for cleaning the tank without killing the fish.

To be clear, if you follow the proper mixing ratio and thoroughly rinse the tank afterward, nothing bad will happen.

Otherwise, it can damage fish skin and gills, leading to respiratory problems, suffocation, and death. This substance is also corrosive, damaging the fish tank.

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  • Mix nine parts water with one part regular household bleach.
  • Pour the solution into a spray bottle, cover it, and shake it very well for at least ten seconds before use.
  • Spray the aquarium surfaces with the bleach solution, allowing it to cover everything.
  • Do the same with aquarium decorations. You can also use this method to sanitize fish tank gravel. However, do not spray bleach on live aquatic plants.
  • Secure the fish tank and decorations to prevent kids and pets from contacting the disinfected aquarium.
  • Set the timer to ten minutes to let you know when to rinse.



[su_box title=”Method 3: Use other fish-safe disinfectants.” box_color=”#d5eaec” title_color=”#013b56″ radius=”0″]


The following solutions are excellent alternatives to vinegar and bleach in disinfecting fish tanks.

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  • 1% benzalkonium chloride – requires more effort for rinsing
  • 1% sodium chlorine + potassium peroxymonofulfate – the safest but priciest solution for fish tank sterilization
  • 2 mg of potassium permanganate for every 4 cups of water – ideal for parasitic infestations
  • 3% hydrogen peroxide – safer than bleach, but could be costly


To clean with any solution mentioned above, just follow the same steps as stated in method 2.


Step 5: Rinse and dry the fish tank and accessories.


Rinsing vinegar off the fish tank and decorations is easier than washing off the bleach. You can use the aquarium almost immediately after rinsing and drying.

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  • Since bleach is tricker, make sure to rinse all items at least twice to remove as much residue as possible.
  • If you can still smell chlorine, submerge the aquarium objects in clean water for several hours before shaking and rinsing them off one more time.
  • Air-dry the aquarium for 24 hours, which should be enough time to break down vinegar and bleach ingredients into safe byproducts.
  • You are now ready to use the fish tank like new. Refill it with treated water and return your fish and other items. Or, you can pack the aquarium for its next owner (if you want to sell it).


Things Not to Use in a Fish Tank

Aquarium experts advise against using ammonia, dishwashing liquid, soap, detergent, and other harsh substances when cleaning fish tanks.

Aquarists should not also use tap water when cleaning fish tanks because it might contain chlorine. Extremely hot or cold water is also a no-no, as the temperatures can break the tank.


You now know how to disinfect a fish tank. Although vinegar is a safe choice, bleach remains the best method for killing germs and other contaminants in the aquarium. However, aquarists must observe the ideal bleach dilution and ensure adequate rinsing to guarantee fish safety.

Alternative methods are available. However, these tricks also use chemicals that some aquarists might not feel confident using in their aquariums for fish safety reasons.