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How To Sterilize A Fish Tank And Equipment – All You Need To Know

How to sterilize a fish tank and equipment

Knowing how to sterilize a fish tank and equipment needed for fishkeeping is a basic skill every aquarist needs to master. Safely sterilizing a brand-new aquarium is the first step you take when getting into the hobby. So, what disinfecting solutions can you use to sanitize a tank without endangering fish?

You can use a diluted bleach solution to sterilize fish tanks and equipment.

There are, of course, some cautionary steps to take and instructions to follow when using bleach as your aquarium disinfectant of choice. We’ll get into all the details later on in the article!

But you should know that there are other fish tank sterilizing solutions to choose from, each with a variable degree of efficiency. The type of disinfectant you use will depend on the reason why you’re “deep-cleaning” a tank or the equipment.

You’re going to need a stronger sterilizing agent (i.e., bleach) when you’re cleaning a contaminated fish tank (after a disease breakout) than you would for casually cleaning a tank that you’re planning to repurpose.

When Should You Sterilize A Fish Tank And Fishkeeping Equipment?

disinfect fish tank vinegar
Neon tetra (Paracheirodon innesi)

We use fish tanks to create mini underwater habitats for our pet fish. By default, fishkeeping tanks don’t need to remain sterile. The presence of bacteria is normal and sometimes even necessary (nitrifying bacteria) for a well-established aquarium.

There are, however, a number of instances when sterilizing a fish tank, and your fishkeeping equipment is vital for the safety of your fish. So, when should you sterilize a fish tank?

First time setting up a tank

You might think that your brand-new tank is as clean as it’s ever going to be, but there is plenty of residue and contaminants lurking on the surface of an off-the-shelf tank, which can mess with your water quality and put your fish in danger.

You should always sterilize a fish tank before the initial set-up. We’ll talk about the most popular solutions you can use to efficiently sanitize a tank in a bit, but keep in mind that all of them include a 24h air-drying period. So, plan accordingly!

Disease

Whether we’re talking about sterilizing a quarantine tank or about deep-cleaning a tank that has been the epicenter of a disease outbreak among your pet fish, sterilizing the fish tank and equipment is definitely necessary.

Even if some of your fish survived, the water quality inside a disease-ridden aquarium will oftentimes be dangerously low, which puts your remaining fish at risk for stress/another disease outbreak.

Here’s how you can start over with a disease-ridden tank:

Parasite infestation | Bacterial infections

Parasites/harmful bacteria that hitchhike their way into your aquarium are notoriously hard to get rid of. That’s why quarantining new fish and live aquatic plants is highly recommended as a precautionary method.

Even if you manage to rid your pet fish of parasites, it’s difficult to tell when the water inside your tank is no longer contaminated. That’s why in extreme cases, sterilizing your fish tank and equipment is the best course of action, just to be on the safe side.

Fungal infections

Fungal infections in fish are tricky to deal with, as they are usually a “secondary symptom” to an underlying condition. Fish with open wounds, contaminated live food, or poor water quality can trigger a fungus outbreak.

Fungi can spread rapidly in an aquarium, so while dosing your fish in a quarantine tank, it’s a good idea to sterilize your tank and the gear inside. A clean cycled tank will give your fish better survival chances after fungal infection.

Neglected tanks passed the point of no return

If you’re trying to “save” a tank that’s been neglected and that’s suffered a biological collapse, a hard reset might be your only option.

Taking everything out, sterilizing all non-porous elements, discarding porous objects (driftwood, filter media, air pump tubing, some types of gravel/substrate, etc.) is the only way to start fresh in this case.

With some far-gone aquariums, you can slowly get them back to life, with small frequent water changes and other maintenance tasks done alternatively. But, if there’s no life left inside a neglected tank, it’s best to just start from scratch.

Sterilizing fishkeeping equipment

Getting into the habit of sterilizing your fishkeeping gear before the first use and when switching the equipment from one tank to the other will save you a lot of time and effort in the long run.

Non-fish-friendly residue leftover from the manufacturing process can make its way into your aquarium if you don’t preventively sanitize your gear. Here’s a list of the equipment you need to sterilize before the first use:

  • Heaters;
  • Thermometers;
  • Filtering systems;
  • Tank lids/hoods;
  • Air pumps/air stones;
  • Powerheads;
  • Light fixtures.

Gear aside, you should sterilize the tools you use for aquascaping. Anything used for general fishkeeping tasks should be sterilized after every use to prevent cross-contamination between tanks. Otherwise, pathogens can get reintroduced in a tank that just got over a disease outbreak.

  • Aquascaping tools;
  • Fish nets;
  • Automatic feeders;
  • Spawning cones;
  • Tank dividers;
  • Breeding boxes;

Accidental contaminations

Ever spilled an entire container of fish food inside your tank by accident? Ever had a kid play “scientist” with the water inside your tank and pour an entire bottle of soda in just to see what would happen? You’re not alone!

Keeping fish tanks in our homes comes with the risk of accidental contaminations, especially if your aquarium doesn’t have a hood/lid. Children, pets, or even clumsy aquarists can accidentally expose the pet fish in a tank to substances that are deadly to them, even in the tiniest concentrations.

The best thing to do if your tank is accidentally contaminated with a harmful substance, or even too much of a good thing (food, medication, etc.), is to quickly remove the fish and place them in a temporary container. Then proceed to sterilize your fish tank and equipment. 

What To Have On Hand When Sterilizing Fish Tanks And Equipment

How to disinfect aquarium nets
Cherry barbs (Puntius titteya)

Other than plenty of clean water, and a designated container that you only use when sterilizing tanks, or fishkeeping equipment, there are a few essential items you should have on hand:

How To Sterilize A Fish Tank

Depending on the reason why you’re sterilizing a fish tank, there are quite a few methods you can use.

The two most popular solutions are the bleach soak/dip and the vinegar soak/dip.

Fishkeepers, especially beginners, are often reluctant to use bleach as a disinfectant. The truth is when done right, sterilizing a tank using a diluted bleach solution is the most efficient way to sanitize an aquarium after a disease outbreak.

Vinegar soaks are a less aggressive sterilizing solution, but they can be perfectly safe for getting rid of mineral deposits and for prepping a tank for its initial set-up.

Regardless of the fish tank sterilizing method you go for, keep in mind that disinfectants should never be used while your pet fish are in the tank. Empty out your tank before attempting to sterilize it!

Here are the 2 most popular methods of sterilizing a fish tank:

Bleach Method

Use a 10% bleach solution to sterilize your fish tank, mix 1 part bleach with 9 parts water, and create a 9:1 ratio (9 cups of water for every 1 cup of bleach).

Depending on what fishkeeping gear you want to sanitize along with your tank, make sure you have enough bleach solution to fully submerge the equipment you need to sterilize.

To sterilize your fish tank using a bleach solution:

  • Fill up a spray bottle with the bleach solution, and spray the interior and exterior parts of your aquarium.
  • Let the bleach solution work for no longer than 15 minutes (10 minutes is enough);
  • Rinse your tank thoroughly using clean water (the most important step of the process!);
  • Air dry your tank for 24 hours;
  • Fill up your aquarium, add a water conditioner to remove chlorine/chloramine residue, and proceed as usual with setting up your fish tank.

FAQ

Q: What type of bleach should you use when sterilizing a fish tank and equipment?

A: Generic household bleach, with a 5-6.5% concentration of sodium hypochlorite, is ideal for this task.

Don’t use bleach gels. Your bleach should pour out of its container like water does.

Q: Can you safely sterilize fishkeeping equipment using bleach?

A: Yes, more on that later on in the article! But the process is the same. You mix a 9:1 bleach solution using bleach and water, and you soak the equipment for 10-15 minutes.

Rinse, rinse again and rinse some more, then air-dry for 24 hours before use.

Q:Is bleach harmful to your tank/fish?

A: When used correctly and diluted sufficiently, bleach is a safe disinfectant to use when sterilizing fish tanks and equipment. Glass panels, fishkeeping tools, some decorations, your heater, filter, air pump, etc., can all be safely sanitized using a bleach solution.

If rinsed thoroughly and air-dried for at least 24 hours, a tank sterilized with a bleach solution is safe for your pet fish as well.

Here are some cautionary warnings you should know about using bleach to sanitize a fish tank:

  • Bleach in any concentration is extremely dangerous for fish. Make sure your pet fish are in a container that’s at a safe distance from the area you’re using when sterilizing the tank.
  • Bleach is a corrosive substance, and it can damage your tank if used improperly.
  • Due to its corrosive nature, bleach can damage/cause discoloration when used to sanitize brightly colored decorations. It can also have the same effect on some porous materials.
  • Don’t mix household bleach with other detergents, tank cleaners, or disinfectants.
  • Always carry out the tank sterilizing task in a well-ventilated area, and take precautions to protect your skin and eyes when working with bleach.
  • Never let your equipment soak for more than 15 minutes in a bleach solution.
  • Don’t use a bleach solution to sterilize fish tank decorations made of porous materials. These can soak up bleach and later diffuse it into the water, putting your fish at risk.

Vinegar Method

Vinegar is the second most popular sanitizer used by aquarists. You can use a 1:1 vinegar solution, mixing clean water and regular vinegar. For limescale build-up, if you have particularly hard water, you can try using a 2:1 vinegar solution (2 parts vinegar to 1 part water).

To clean your fish tank using a vinegar solution:

  • Transfer the vinegar solution to a spray bottle, and spray down your tank generously. Let the solution sit for anywhere between 10 minutes and a few hours, depending on the state of your aquarium.
  • Soak your fishkeeping equipment in the vinegar solution for at least 10 minutes. You can leave your gear to soak for up to 3-4 hours for tougher mineral deposits.
  • Rinse your tank and equipment thoroughly.
  • Air dry for 24 hours.
  • Fill up your tank, and add a water conditioner before reintroducing your fish.

Other Tank Cleaning Methods

Zebrafish
Zebrafish (Danio rerio)

Here are some less popular fish tank sterilizing methods, that are considered safe to use in fishkeeping, according to CA Fish Vet:

  • Benzalkonium chloride

Benzalkonium chloride is the active ingredient in Lysol®. It works by dissolving the fatty outer layer of bacteria cells, making it easier to efficiently sterilize a fish tank.

It can be harder to rinse off, but it’s also more effective at getting rid of Mycobacterium marinum than bleach is. It should be used in a 1% concentrated solution.

  • A mix of potassium peroxymonosulfate & sodium chlorine

Also known as Virkon® Aquatic, this disinfectant is among the priciest solutions you can use to sterilize a fish tank. It’s used by fish breeders, and it’s considered one of the safest aquatic disinfectants you can use.

It should be used in a 1% concentrated solution.

  • Potassium permanganate

Potassium permanganate is used mainly as an aquarium treatment, meant to rid a tank of a parasitic infestation. It works through oxidation, destroying most cells, leaving the treated water pink/brown during the sterilization process.

A potassium permanganate (KMnO4) solution can be made by combining 2mg of KMnO4 with 4 cups of water, which can then be mixed into the treated water to remove parasites.

  • Hydrogen Peroxide

Although hydrogen peroxide is easily accessible and considered a safer disinfectant than bleach, it’s significantly more expensive than bleach.

It’s considered safer because, after 24 hours, hydrogen peroxide breaks down into safe elements (water and oxygen), eliminating the risk of residual contamination.

It can be used to sterilize a tank in a 3% concentrated solution.

How To Sterilize Tank Equipment

You can safely sterilize most items in your fish tank using a 10% bleach solution.
The list of tank equipment you can sanitize this way includes gear made of non-porous materials:

  • Heaters;
  • Filtering systems;
  • Thermometers;
  • Powerheads;
  • Air pumps;
  • Air stones.

Follow the same steps listed above for tank sterilization:

  • Soak fish tank equipment for 10-15 minutes in the disinfecting solution;
  • Rinse thoroughly;
  • Allow to air dry for 24 hours.

There are a few things inside your tank that you should avoid cleaning via bleach solution.

These items are better suited for cleaning with a vinegar solution:

  • Artificial plants (both plastic and silk);
  • Porous/brightly colored decorations;
  • Wood;
  • Gravel, rocks, and/or colorful substrate;
  • Any other items made of porous materials.

Vinegar is a better option for these items because bleach would cause discoloration in the intensely colored ones, and it might get soaked up and later released by the porous ones.

For gravel and rocks, you can go as far as boiling them for 10-20 minutes in tap water to make sure they’re pathogen-free especially if you’re reusing the gravel from another tank.

Let the rocks/gravel cool down completely, and allow them to air-dry before introducing them into your tank.

How To Sterilize Aquarium Fish Nets

It’s recommended that you sterilize aquarium fish nets after every use. But how do you do that if cleaning your gear (and air drying it) takes 24 hours?

Use a max. 3% hydrogen peroxide solution to disinfect your aquarium fish nets after every use.

In this concentration, hydrogen peroxide is harmless to fish, as it decomposes into just water and oxygen without any dangerous residue. An ideal disinfectant for an aquatic hobby!

Conclusion

As you can see, you can safely sterilize a fish tank and fishkeeping equipment with some pretty basic solutions that you most likely already have in your household.

Make sure you mix the disinfecting solutions in the proper concentrations and follow the rinsing & air-drying instructions before reintroducing your fish to the cleaned tank.

Keep in mind that sterilizing an aquarium should only be done in exceptional situations, not as a regular cleaning routine. Your fish tank is meant to be full of life, bacteria and all!


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