Using Hydrogen Peroxide to Clean Your Aquariums – A Comprehensive Guide

Home-aquariums are striking household decorations. You may know someone or have it yourself.

But here is the catch- not many people can afford the time or the resources to build a beautiful aquarium.

Especially for people like us, it becomes tough to keep up with daily cleanings and maintenance when we do not know the proper techniques.

The goal to have a gorgeous and appealing aquarium is to be efficient with its cleaning. Here methods like using hydrogen peroxide come in handy.

Hydrogen peroxide is a chemical that has remarkable bleaching properties. Not only can it remove stains and dirt, but it has excellent anti-algal and anti-fungal properties.

Moreover, if you think that algal growth can be removed by vigorous scrubbing, you are mistaken. Using bleach, on the other hand, can put the sea creatures in jeopardy.

More often than not, hydrogen peroxide provides a middle ground. The only solution to get a clean and inhabited aquarium is by using hydrogen peroxide!

How Often Does One Need to Clean Their Aquarium With H2O2?

Hydrogen peroxide is a chemical compound having mild antiseptic and strong bleaching properties.

It is used on the skin to prevent infections from cuts, scrapes, or burns in a clinical setting. Some people also use it as a mouth rinse to help remove mucus or relieve irritation (due to cold sores/gingivitis) (Jeez!)

This chemical works by releasing oxygen, which can cause foaming. This can further and react with infections and clean the area as well as remove the dead skin.

But how are these mad-lads used for aquariums?

According to many experts and forums, hydrogen peroxide in small enough amounts can kill the growing algae in an aquarium. As well as preserving the lives of your fishes.

Hydrogen peroxide cleans by releasing harmless oxygen and water. So the only way your fish would be at risk would be through oxygen overdose.

Although it depends on the type of algal infestation, you have in your aquarium. The blue-green algae are tough to remove, so they require more hydrogen peroxide than green algae.

But it is safe to assume, one dose per day should be enough for your aquarium.

Beware that hydrogen peroxide is caustic and can kill your plants or burn your fishes’ lungs if not added in a calculated amount.

What Causes the Odor Coming From the Aquarium?

The main culprit of the foul odor coming from your aquarium is decomposing bacteria.

Bacteria attack and feed on the dead organic matter they can find. While doing so, they release many foul-smelling products such as ammonia. But can you blame the bacteria? Poor guys are just hungry.

On a broader scale, anything that leads to the accumulation of organic matter in your pond can cause an odor.

Most commonly, it is because of excessive food granules in the water that start to rot. And in those aquariums that aren’t cleaned properly, the accumulation of fish waste can lead to a foul odor.

However, it can be due to dead fish or plants present in your aquarium in some cases.

Why is Hydrogen Peroxide Suitable For Cleaning Aquariums?

Aquariums are ultimately a living habitat.

Using biotoxic products such as bleach can contaminate the water. In addition, the byproducts produced are fatal to the fishes and plants present.

Hydrogen peroxide, on the other hand, is highly unreactive and decomposes quickly. Thus, making it safe to use because it decomposes into harmless oxygen and water in about 24 hours.

Antibacterial Properties

Just like bacteria attack and cause diseases in humans, the aquarium habitat is no exception.

Bacteria like Aeromonas are very common in fish aquariums. This germ is responsible for causing discoloration in the limbs of fishes and amphibians. It may even lead to internal bleeding in these animals.

The organic action of hydrogen peroxide provides the solution for this. Hydrogen peroxide liberates reactive oxygen in the aquarium, which overloads the bacteria.

By adding a calculated amount of hydrogen peroxide, you can effectively kill these bacteria without risking the animals. In addition, it gives a far better alternative than using chemicals such as chlorine or bleach.

Excellent Disinfectant

Some of the common fishes’ diseases include fin rot disease, swim bladder disease, and vibriosis. All of them are caused by some species of bacteria.

Many of the aquatic bacteria that infect fishes use oxygen to survive. However, the amount of oxygen is minute and regulated.

By using a bit of chemistry, we can specifically target the aerobic (oxygen-loving) bacteria.

Hydrogen peroxide reactive oxygen in the aquarium habitat. This oxygen is too much for the tiny bacteria, and instead of utilizing it, they start to get overloaded. In addition, many of the enzymes present in the bacteria change their nature after reacting with oxygen (oxidizing) and thus inhibiting its essential functions.

Large animals such as fishes can easily use this free oxygen (if given in a calculated amount). Hence, hydrogen peroxide becomes a fantastic disinfectant that only kills parasites. (Crazy, I know, right!)

Helps Removed the Foul Smell

One of the other advantages of using hydrogen peroxide is how it removes the odor. And the working behind it is introductory 12th-grade chemistry.

We smell the odor because of the inevitable byproducts bacteria produce while decomposing dead organic matter in aquariums. They include ammonia, aldehydes, and sulfides.

The excess oxygen released by hydrogen peroxide reacts with these byproducts. And thus, they turn into odorless oxygenated species (nitrates and carboxylic acids).

Hydrogen peroxide can, of course, provide a natural and harmless way of removing the odor from the aquarium.

Anti-Fungal Properties – The Most Important!

One of the most ground-breaking reasons to use hydrogen peroxide is its efficacy in killing fungi growth in aquariums.

Where common disinfectants such as bleach and chlorine are proficient in killing bacteria and algae, they become useless against these ugly-looking creatures.

Hydrogen peroxide, because of its organic nature, can effectively kill fungi and bacteria alike. Some of the common aquarium fungi include:


Saprolegnia is a family of freshwater molds that are very common in household aquariums. Unfortunately, they can infect almost all species of fish, making them a nuisance.

Saprolegnia is known to cause “Cotton wool disease,” which is whitish fur-like growth in fishes. They have a solid affinity for vitamin C-rich foods.


This is a relatively uncommon fungus in aquariums but becomes deadly once it infects a fish.

Branchiomyces are known to cause “Gill-rot disease” in fishes in which the gills of the fishes are covered with mucus and appear rotted.


Achyla refers to a notorious family of water molds that commonly attack the eggs of fishes.

An achyla infestation can lead to “egg fungi” disease in fishes. This is because the rapid breeding of fungi attacks the unhatched eggs of fishes. And once the egg is entirely infected, there is no cure.

What’s the Ideal Concentration of Hydrogen Peroxide for Cleaning Aquariums?

There are many different sources and opinions about how much hydrogen peroxide you should use in order to disinfect your aquarium properly.

Some people like to go overboard and use as much as 20 ml per gallon of water, while some use as little as 0.5 ml per gallon of water.

It is essential to calculate the amount of hydrogen peroxide used correctly. There are different hydrogen peroxide concentrations available in the market. Starting from 1% up to 90%, which is used in rocket fuels. The most commonly available concentration is 3% hydrogen peroxide solution.

The agreeable amount of hydrogen peroxide is 1 ml per gallon of water of 3% hydrogen peroxide solution. In addition to that, you must do a significant water change after adding the chemical.

Various algal infestations require hydrogen peroxide concentration accordingly. However, if you feel a little too nasty, the amount you use should not exceed 1.5 ml per gallon of water.

The goal is to eliminate foul parasites while maintaining the ecosystem of the aquarium. Too much hydrogen peroxide can kill good bacteria in aquariums that produce oxygen, nitrogen, and essential nutrients for fishes. Lack of oxygen and minerals can jeopardize animals in the long run.

Make Sure to Calculate the Amount You Need to Put In!

Now, I know it is very tempting to empty the whole bottle of that sweet hydrogen peroxide (it’s not tasty, by the way) into your aquarium but wait. You can either empty the aquarium and use hydrogen peroxide as cleaning spray or directly inject it into the water.

In most cases, you should do the former as it is much safer for aquarium habitat. However, if you face algal growth on plants, then 1 ml per gallon of water is the way to go.

The first step is to know the capacity of your aquarium.

And don’t worry if you don’t. Grab a meter tape and follow along:

  • Measure the length, width, and height of your aquarium
  • Multiply them
  • Convert the meter cube into gallons on google

And that’s it!

The most commonly available aquarium ranges from 10 to 29 gallons. Therefore, you need to put in hydrogen peroxide accordingly.

Also, take into account the objects and plants you have in your aquarium. We need 1 ml per gallon of water, so be 1 ml lenient when putting in, just to be safe.

Using Hydrogen Peroxide to Clean Aquariums is a Piece of Cake!

After taking in the calculations and buying a dozen bottles of hydrogen peroxide, let’s see how you can go about killing those nasty bacteria and algae. (Fungi if you are unfortunate enough)

Making the Solution

To make a hydrogen peroxide solution, all you need is a syringe for measurements. And, of course, water and hydrogen peroxide itself.

Take into account what concentration of hydrogen peroxide you have available and extract the hydrogen peroxide solution into the syringe accordingly (e.g., 0.1 ml of 30% solution of hydrogen peroxide is enough for 1 gallon)

Steps for Cleaning

Now that you know how vital hydrogen peroxide is, let’s see how you can use it.

The first way is to clean it by emptying the aquarium

  • Extract hydrogen peroxide from the bottle using a syringe
  • Pour it into a spraying bottle and then dilute it using water
  • The dilution should depend upon how deeply stained is the aquarium
  • Using the spray and a clean cloth, remove the stains
  • Do not forget to clean the edges thoroughly
  • Let it dry in the sun before you fill the tank back

And that’s about it for cleaning a dry tank.

For tackling the algal growth, you have to use a full tank. The procedure is as follows:

  • Calculate the amount of hydrogen peroxide you need according to your tank
  • Extract the amount using a syringe
  • Before injecting it directly into the tank, take some water in the bowel and pour it in.
  • Slowly pour the solution into the tank while making concentric circles
  • Leave it for an hour and monitor the bubbling
  • Remove them if the animals show signs of struggle (trying to come up to the surface).
  • After the bubbling stops, change the water and put the animals back in

And that’s how easy it gets!

Moreover, if you see an algal growth feel free to pour the calculated amount directly over it instead of making a solution and filling it in a tank.

Is Hydrogen Peroxide Safe? Is it Stable in Water?

Ready for some nitty-gritty?

The stability of hydrogen peroxide depends on various factors: pH, the temperature of the water, the sunlight, and enzymes. The high concentration of these factors can accelerate the dissociation of hydrogen peroxide. Therefore, it is crucial to know the stability of hydrogen peroxide to avoid excessive exposure.

According to a study, at 15-20 degrees Celsius, the amount of hydrogen peroxide put in the tank (10 ml) was gone by 2-3 days, in the presence of aeration and organic material.

However, in stagnant water with no aeration, the concentration of hydrogen peroxide was measured to be half of its initial concentration and measured till day 10.

Hence, hydrogen peroxide contraction appears to be affected by the aeration and availability of organic material (increased dissociation in presence). However, specific fish sensitivities and initial concentration put in also determines its toxicity to the habitat.

Is it Legal to Use for Aquaculture?

Hydrogen peroxide and its implications feel too good to be true. So is it legal to use?

In 2007, FDA approved PEROX-AID® (yay!) for:

  • Mortality of freshwater reared fin-fish eggs due to saprolegniasis (the cotton wool disease fungus)
  • Mortality of freshwater-reared salmonids due to bacterial gill disease
  • Mortality of freshwater-reared cool water finfish and channel catfish due to external columnaris

However, no other form of hydrogen peroxide was declared legal for the use of fish. (No! You can not use 90% rocket fuel hydrogen peroxide for green algae)

Does it Have Any Side Effects on Fishes?

On paper, hydrogen peroxide looks like the perfect tool for cleaning the aquarium and removing unwanted pathogens, with its natural killing abilities using harmless product oxygen.

However, like all things, hydrogen peroxide can too have side effects on fishes and aquatic life if it is abused.

Some of them include:

  • Recent findings show that hydrogen peroxide can be harmful to the mucosal linings of the gills, skin, and gut in fishes. It takes about two weeks for fishes to recover from the damage entirely. However, they can be highly susceptible to pathogenic attacks in the meanwhile.
  • Data from another research suggests stunt growth in fishes due to hydrogen peroxide.
  • Some fishes such as Blue gourami and suckermouth catfish are allergic to hydrogen peroxide. In the experiment, these species of fishes did not tolerate even the low concentrations for 1 hour.

The side effects of hydrogen peroxide only seem to appear when it is used more than its required amount. And even then, the benefits of using it outweigh the side effects.

In the studies mentioned above, the appearance of diseases due to bacteria or fungi remained the same, if not decreased.

Allowing us to believe that hydrogen peroxide may weaken fishes a bit, but it protects them from pathogens even more so.

Hydrogen Peroxide and Crystal Clear Aquariums – The Takeaway

While there are many hobbies, maintaining an aquarium is one of the more intriguing ones.

A well-maintained aquarium gives a luxurious appearance to the house. However, in many cases, people are not aware of the steps and tools required for the process.

Hydrogen peroxide is the emerging savior of all fish-tank enthusiasts. With its natural killing properties and ability to dissociate into harmless byproducts, it has quickly become a favorite.

By understanding how this compound works and calculating the dose, people can effectively kill any algal or fungal growth in their aquariums—and conserve the health of their fishes while doing so.

Bleach and chlorine are the tools of the past. So, order your set of hydrogen peroxide bottles now!

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