How to dechlorinate tap water for fish tank?

When setting up an aquarium, you need to have a very careful plan. To have a healthy aquarium, factors such as temperature, type, number of fish, and number of plants are very important.

Also, you need to pay attention to the source of water you use for the aquarium. Most people will use tap water for their aquariums.

Therefore, you need to know how to dechlorinate tap water for a fish tank. Because chlorine will harm your fish.

Why is there chlorine in the water?

Today, domestic water is supplied by water treatment plants. Water taken from rivers and lakes is put through filters to remove objects from large to small.

Your local water company will then add chlorine or chloramine to the water to get rid of bacteria or other small life forms that could be harmful to you.

Contact your local water treatment company to learn more about what has been put into your water.

Why dechlorination?

Water purification additives such as chlorine and chloramine are not enough to cause harm to humans but are very toxic to your fish.

Chlorine in water will cause fish to burn, especially in sensitive areas such as the eyes and gills.

Worse, when Chlorine penetrates inside the fish’s body, this will lead to the fish getting full body burns.

At mild levels your fish will be stressed, at heavy levels, your fish will quickly lose their lives.

Therefore, make sure that your water has been chlorinated before pouring it into the aquarium.

Why dechlorination?

Effective methods of dechlorination

Exposing water to the air

This is the simplest method to remove chlorine from water. However, they are only effective with chlorine-only water without Chloramine.

First, prepare an open container, and fill it with water.

Leave the water in an open container for at least 24 hours. During this time, the chlorine will escape into the air. This process is called water aging.

After completing this process, your water is safe to add to the tank.

However, before you put it in the tank, you need to make sure that the parameters such as temperature, salinity, and pH are at the appropriate threshold for your tank.


It is also a simple and effective method of removing chlorine. You only need to boil water for about 25 minutes is enough to remove all the chlorine in the water.

At high temperatures, the rate at which chlorine is released from the water will be faster. This method is very suitable for those who do not have time to wait.

And this way is also extremely economical. Always remember to let the water cool down to the proper temperature before adding it to the tank. As with the above method, boiling cannot remove chloramines.

Using ultraviolet light

Another effective way to remove chlorine is to use ultraviolet light. One advantage of this method is that both chlorine and chloramine can be removed.

The UV lamps emit ultraviolet light with a wavelength of 254nm with a radiation density of 600ml when shining into the water, which will kill bacteria and remove chlorine and chloramine from the water.

They are really effective in dechlorinating and eliminating chloramine in the aquarium water and then you can use them to disinfect the water in your aquarium.

To take full advantage of UV rays. You should combine this with the method of leaving the water outside for 24 hours.

Put water in a container, add a UV light on it and leave it there for 24 hours. Once done, you can rest assured that chlorine is not present in your water.

The good news is that you don’t have to spend a lot of money to buy a UV lamp and they even come built into some tanks.

Effective methods of dechlorination: Using ultraviolet light

Vitamin C

Vitamin C is essential for human health. It helps people fight diseases.

But for aquarists, Vitamin C also has another important use which is to remove chlorine and chloramine from the water.

This method is also chosen by many people to use because it is also very simple to perform.

You simply add Vitamin C to the water you intend to put in your aquarium and it will neutralize the chlorine in it. The right dose to remove chlorine from water is one teaspoon of Vitamin C containing ascorbic acid per 1 gallon of water.

Note, that the use of Vitamin C can affect the pH of the water, so consult the experts at your pet store for your tank.

Use bottled water

Bottled water produced by reputable brands is safe for humans and will not contain substances harmful to your fish. So it is also a reliable choice for aquarium water.

However, it will be a bit expensive if the amount of water you need is large and it will need to be replaced periodically.

For nano-tanks, this method is also very suitable.

Effective methods of dechlorination: Use bottled water

A carbon filter or reverse osmosis filter

Reverse osmosis filters have been widely used around the world for the purification of drinking water. They work by using a pressurized pump that pushes water through a semi-permeable membrane. Toxic substances will be retained there, including chlorine and chloramine.

Similar to reverse osmosis filters, carbon or activated carbon filters are also capable of removing chlorine, chloramines, and some other harmful compounds from water.

As the water passes through the Carbon filter, the carbon layers trap all the harmful chemicals. Carbon blocks or activated carbon are also commonly used as filter media for aquariums.

This method may cost you more but it is very effective.


The use of chemicals known as water conditioners will help you remove chlorine and chloramines from water quickly and effectively.

However, inside these chemicals, there are many chemical components that are not beneficial to the health of aquarium fish. They can even make your fish sick.

Therefore, when you need to remove chlorine from water, consider the natural methods outlined above first.

This way your fish will live normally and healthy in your aquarium, without any problems from the water environment they live in.

If you still want to use chemicals, talk to a professional to find out which one you should use.

Eliminating chloramine

Today, Chloramine is a fairly common chemical additive. It is used by many water plants as an alternative to or in conjunction with chlorine for water treatment. In water, chloramine lasts longer than chlorine and is more difficult to remove. Chlorine can dissolve into the air, but chloramine can’t no matter how long you leave the water in.

Therefore methods such as freezing or boiling will not be able to remove chloramines.

Methods that can safely and effectively remove chloramines from water are the use of ultraviolet light or the use of carbon filters.

What you need to find out now is whether your domestic water source contains chlorine or chloramine or even both, you should contact your local water treatment plant to find out exactly what that is.

How to treat fish with chlorine poisoning

Chlorine poisoning in fish is a common problem faced by novice aquarists. They often ignore the problem of needing to remove chlorine from the water before pouring it into the aquarium.

Tap water will be directly filled into the aquarium without any treatment, leading to chlorine poisoning.

Chlorine poisoning is often fatal to fish if not detected and treated promptly.

How to treat fish with chlorine poisoning

Identification of chlorinated fish

When fish are poisoned with chlorine, they will first encounter respiratory problems such as suffocation, and irregular breathing. Affected fish may swim irregularly, hovering near the surface of the water.

The fish may appear pale, look like it is covered with mucus, or appear abnormal red areas on the body.

Water and fish treatment

If you suspect your fish has chlorine poisoning, remove the fish from the tank as soon as possible.

You need to set up another tank that is safe and fully functional.

The water used in this tank must not contain chlorine. You’re better off using treated tap water or bottled water.

Supplement nutrients and minerals to feed fish and aquatic plants.

Use a racket or net to remove each fish from the chlorine-free tank, then gently release it into the new tank.

Currently, there is no drug that can fix the damage that chlorine causes to fish. You can just take them out of the chlorine reservoir and let them heal on their own.

Cases of fish living in a chlorinated environment for a long time will often cause them to die because the chlorine has severely damaged their gills.

Preventing Chlorine Poisoning

Never use tap water that has not been treated to remove chlorine from your aquarium.

If you use chlorine-containing cleaners to clean or disinfect your aquarium supplies. You need to rinse those items with clean water carefully before putting them in the tank to prevent the water from becoming chlorinated.

Also, you can use aquarium test strips to check the chlorine in the tank. This should be done on a regular basis to promptly identify problems in your tank.

Preventing Chlorine Poisoning


Thus, I have introduced to you simple and effective ways to remove chlorine from water.

Of these, there are ways to remove only chlorine and there are ways to remove both chlorine and chloramines, some are free, but there are also ways that you have to pay.

But in general all show effectiveness in removing chlorine.

And again, consider carefully before choosing to use chemicals to remove chlorine.

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