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How Long Does Water Take to Dechlorinate ? 7 Best Ways

How Long Does Water Take to Dechlorinate? If you are a fish lover and planning to build an aquarium, there are a few things you should consider first. Water is definitely one of them. Regardless of the aquarium type (freshwater or saline water), you must use chlorine-free water. Otherwise, your fish have to face many problems.

So, this guide will exactly tell you how to dechlorinate?, How many chemicals to add? , How to test your water for chlorine. If you follow this advice your fish will never die from chlorine.

How Long Does Water Take to Dechlorinate _

So How Long Does Water Take to Dechlorinate?  It will take 1 to 5 days or 24 to 120 hours to completely dechlorinate the water (tap water) if it sits in the tank. In municipal water chlorine levels of 1.5 to 2.0 ppm but it can change.

So We cannot tell an exact period because it depends on the initial chlorine concentration in water, water temperature, water volume, chemical properties of water, and tank filter type. Also, keep in mind that 0.1-0.3 ppm chlorine levels are lethal to most fish.

So it is essential to remove Chlorine from the water before introducing fish into the aquarium. Chlorine can remove from water using different methods. Now in this article, we are going to discuss some ways to remove Chlorine from water.

Table: How Long to Dechlorinate

Dechlorinate MethodTime
Keep in a storage tank1 to 5 days
Boiling the water for Dechlorinate8 minutes
Remove Chlorine by Aeration12 to 24 hours
Ultraviolet light to dechlorinate5 minutes
Water softenerDepends on type
Ascorbic acid / vitamin c5 minutes
Dechlorination water conditioner5 to 30 minutes
Homemade dechlorinator5 to 30 minutes
How to remove Chlorine from tap water infographic

How do dechlorinate the tap water? (ways to remove chlorine)

Natural methods to remove Chlorine from tap water

Keep in a storage fish tank

We are going to talk about the easiest and most inexpensive method first. It is to keep tap water in a storage tank to remove Chlorine.  Although this process is affordable, the process takes a long time.

How long does it take for Chlorine to evaporate from water for fish? The time of storage can be varied from 1 to 5 days.

The storing time depends on chlorine concentration in the tap water. For example, if the chlorine concentration is 2 ppm (parts per million), you leave the water for at least 110 hr. to remove chlorine in tap water.

But there is an important point you should keep in mind. It is documented that Chloramine can not remove only with evaporation. To remove Chloramine, you have to heat the water or other methods.

 What is Chloramine?

Chloramine is a chemical that forms in tap water when Chlorine reacts with ammonia in water. Chloramine is also toxic to fish. Most of the time, it is available in tap water due to chlorine usage in tap water disinfection. Sometimes Chloramine is directly added to the water of highly populated areas because it is a more efficient disinfectant. It is deadly to fish because it can absorb through fish skin and destroy cells.

Chloramine vs Chlorine.

chlorine or chloramine may sound like the same thing, But they are different from each other. It is a variant of Chlorine that has ammonia in it. Chloramine stays in water more active than Chlorine. But Chloramine is toxic to fish compared with Chlorine.

How long does it take for Chlorine to evaporate from 1 gallon of tap water

it takes 1 to 2 hours to dechlorinate the tap water, but it will not remove Chloramine from tap water. It can take up to 4 days. But you can dechlorinate and removes Chloramine quickly if you use dechlorinator. If you boil 1 gallon of water, it can take up to 8 minutes to dechlorinate. For 10 gallons of water, it will take more time.

Boiling water for Dechlorinate

As I mentioned earlier, evaporation only removes chlorine in tap water. Chloramine, a chemical by-product of Chlorine, did not evaporate as easily as Chlorine. It remains in the fish tank. To get rid of Chloramine, you need to boil the water. Boiling will get rid of it faster than Chlorine. It is also believed boiling will produce enough kinetic energy to remove Chlorine from the water effectively. Boiling will reduce the holding capacity of dissolved gases in water.

Boiling 10 gallons of tap water for about 8 minutes will eliminate 1ppm of Chlorine from the water and is safe for fish, boil for 20 minutes.

Chloramine is a more stable chemical than Chlorine. Therefore it will take much more time to evaporate from the system. It will take around 1 hr to remove Chloramine from the same volume of water. So chlorine evaporates boiling 20 minutes enough.

This method is not suitable for a large amount of water. If you have a large aquarium and need a lot of Dechlorination, you should partially do one batch.

Remove chlorine and chloramine by Aeration

An air pump will help you to dechlorinate tap water. When water is aerated through the air pump, it gets rid of Chlorine mechanically. The aeration created by the pump helps to get rid of Chlorine In the water. A pump will not be an extra burden for you since aeration is needed to keep the water circulating. The size of the aeration pump will depend on the aquarium size.

If you have a bigger fish tank with a large amount of water, you need a heavy-duty pump.

How long to dechlorinate with an air pump

It takes 12 to 24 hours under normal conditions, but it depends on the water condition and chlorine concentration in the water. The aeration can indeed accelerate the dechlorinate process because it increases water circulation.

Ultraviolet light to dechlorinate

This is an expensive method to remove Chlorine from your aquarium water. You have to purchase a UV light for this method

The amount of light needed for Dechlorination depends on your aquarium’s size (amount of water). The large aquarium needs a significant UV light source. The length of the Dechlorination relies on the level of organic matter in the water.

Is Ultraviolet light remove Chlorine?

Yes, it can. UV light dechlorinates tap water by attacking chlorine molecules with ultraviolet rays. The UV light will remove both chlorine and chloramine from tap water when correctly set up.

They also have the added advantage of handling and making tap water straightforward and safe to fish. If you are using UV light dechlorination, make sure it can emit 254 nm wavelength and a density (radiant) of 600 ml because it can remove chemicals.



Chemical method to dechlorinate

Use water softener

A water softener will not work well without a filter. If you only use a softener, it only removes magnesium, iron, and calcium. You should use a recommended filter to eliminate Chlorine from your aquarium. But some water softeners claim to remove chlorine and chloramine from tank water by mixing water softener resins with Granulated Activated Carbon (GAC).

The problem is Granulated Activated Carbon (GAC) only removes Chlorine for 1 to 2 years. But softener resins will last for 10 years. The filter will stop removing Chlorine in 2 years while the filter lasting 10 years. It is better to use the activated carbon filter separately.

Another recommended excellent chlorine removal is the KDF-55 filter media, which is granular and can remove large amounts of Chlorine. For better performance, you should place the filter inside a media guard. Chlorine-free water will come out of the filter. It uses redox reactions to remove Chlorine from tank water. It is common to use KDF-55 with an activated charcoal filter because it can extend the activated carbon lifetime by 90%.



Does Water Softener Remove Chlorine?

Some water softeners mixed with activated Carbon or KFG 55 remove Chlorineing from water, but Water Softener resins in self-dose do not remove Chlorine from water. So make it contains activated Carbon.

Does Carbon filter Remove Chlorine?

Your carbon filter will use adsorption to remove harmful material in the water filter consisting of porous material and toxic substances trapped in these pores. A carbon filter is commonly used to clean drinking water.

\We can use carbon filters to purify aquarium water, especially chlorinated water. It is also essential to remove Chloramine from the water. If you use your home water supply to fill the aquarium and already have a charcoal filter, you do not have to worry about chlorination. But if you do not have a carbon filter stored, you should consider buying one before introducing fish.

You can easily buy an activated charcoal filter from a shop. Make sure the one you buy is with suitable quality materials. You should monitor the pH value of the water after every filter process.

Whole House Pre-Reverse Osmosis RO, 20 Replacement Carbon Water Filters CTO GAC


Does vitamin c Remove Chlorine?

Vitamin C is the safest chemical method for neutralizing chlorine, and Chloramine only takes a few moments. It is also known as water-soluble Ascorbic acid, or Vit C. we can also use sodium ascorbate. Vit C is not harmful to organisms in the amounts used for dechlorinating water. At the same time, ascorbic acid is slightly acidic and lowers the treated water’s pH in large doses.

But sodium ascorbate is neutral. So It does not affect the pH of the treated water. If stored in a cool, dark spot, both types are stable, with a shelf life of 1 year in dry form. However, once it is mixed into the solution, vit C degrades in a day or two.

So it is not ideal to use a pre-mixed vitamin C solution. Also, Vit C will not reduce dissolved oxygen in the water as sodium thiosulphate which is another chemical used to Remove free Chlorine

Ascorbic acid + Hypochlorous acid → Dehydroascorbic acid + Hydrochloric acid + water

Dosage if vitamin c to remove Chlorine?

Per 100 gallons of water, you need to add 1 gram of ascorbic acid to neutralize 1 milligram per liter of Chlorine. This reaction is very rapid. you can calculate the same for 10 gallons of water. In other words, the neutralization of 1 part of Chlorine needs approximately 2.5 parts of ascorbic acid. Since ascorbic acid is weakly acidic, the pH of the water treated can decrease slightly.

How to use vitamin c?

To neutralize free Chlorine, sprinkle ascorbic acid on the water’s surface and stir for a few minutes. Chlorine will not dissolve in water. The chlorin precipitation will deposit at the bottom of the fish tank. This method is straightforward to use and less expensive. You can find ascorbic acid in any pet store.

Both chlorine products (Chlorine and Chloramine) will remove from this method. Since this reaction did not reduce dissolve oxygen in the tank.It is also beneficial for aquarium fish and plants. To be safe for fish allow it to react with water for 20 minutes.

Dechlorination water conditioner

Water conditioners are chemical formulations that use to condition the tap water before adding to an aquarium. A simple conditioner can contain dechlorinators. These products can remove Chlorine from your fish tank in a very short period. You can buy these products in many aquariums and online stores.

How to use Dechlorination Conditioner?

Each dechlorinator is slightly different in the dosage recommendations, so you need to refer to the label on the dechlorinator you have purchased. However, most decent dechlorinators are dosed between one drop for every two gallons of water and two drops for each gallon of water. It is simple as that.

How Long Does Water Conditioner Take To Work?

As soon as they come into contact with the chlorine and chloramine molecules, it breaks them down. However, if the water is not circulating, this may take some time. But to be safe, it is recommended to mix Dechlorinatior or Conditioner with water and aerate it for 30 minutes allowing water to circulate.

That ensures all the Chlorine is neutralized. This enables the dechlorinator to remove chlorine molecules by coming into contact. Now the water should be safe to add to the aquarium.

Use a dechlorinator when the new water is in the tank.

You just need to treat the new tap water you are adding to the tank; you do not need to treat the entire tank volume unless you are filling the tank for the first time.

Is dechlorinator/ Conditioner safe for fish?

Ideally, no. They should not affect the chemistry of water and should not involve other additives that you use. The more “extra things” your dechlorinator does, however the more likely some problem could occur. Also in small fish tanks without a filter, it can leave a residue. But it depends on the type of dechlorinator/ Conditioner used. Carefully follow package directions and always clean and maintain filters.

Homemade dechlorinator

You can use sodium thiosulfate to make your own Homemade dechlorinator. It is way cheap that once you buy from the shops. sodium thiosulfate is the easiest and most efficient way to extract Chlorine and Chloramine from your water. Both of them contain sodium thiosulfate, which reacts to form harmless chloride ions with Chlorine (or the chlorine part of the Chloramine).

A range of approximately 2 to 7 parts of sodium thiosulfate is usually proposed to neutralize one part of Chlorine, such as neutralizing 1 litre of a 200 ppm chlorine solution, requiring approximately 0.4 to 1.4 grams of sodium thiosulfate to neutralizing one gallon of a 200 ppm chlorine solution,

sodium thiosulfate

There are many other types of homemade dechlorinators, but we are not sure about usability because most of them are not correctly tested. It is better to stick with traditional, well-known methods to be on the safe side.

How to know if the water is dechlorinated

Chlorine test kit

No matter what method you use to remove Chlorine from water, you should have a chlorine test kit to test the water’s chlorine level. In that way, you can try the variation of chlorine levels by using the test kit. The time you have to spend in Dechlorination is depended on the chlorine concentration in the water.

Once you select the dechlorination process, you can start Dechlorination. After the process, you can check the water by using the chlorine test kit. If the chlorine level is lower, you can move to the next step of building an aquarium. But if the chlorine level is still high, you have to go for another dechlorination process.

It is essential to remove not only Chlorine but also Chloramine from your water. Otherwise, fish will be negatively affected by harmful chemicals. So it is necessary to check both chlorine and chloramine levels in the water.

Introducing fish after Dechlorination

You can introduce fish into the dechlorinated water after checking the Chlorine and chloramine level. But monitoring fish behaviour is essential at least for 2 hours. If fish behave strangely immediately, remove fish from the tank and check for the water’s pH level. Sometimes Dechlorination can cause a low pH level. But this happens very seldom.

Is fish are suffering from too much chlorine?

Chlorine-affected fish may look pale, appear to be coated in mucus, and grow red areas on their bodies. Affected fish can swim erratically or hover, gasping for breath at the top of the tank.

Can water dechlorinate in the sun?

It takes 24 hours under normal conditions, but it depends on the water condition and chlorine concentration in the water. The aeration can indeed accelerate the dechlorinate process because it increases water circulation.

Dechlorinate tap water with an airstone

Under normal conditions, It takes 12 to 24 hours. The aeration can indeed accelerate the dechlorinate process because it increases water circulation. but this is not a fast method for dechlorinate water.

How long can fish survive in chlorine water?

The answer is Immediate. The fish gills are very susceptible to Chlorine so they will not survive in chlorine water.

But in lower concentrations of Chlorine, they can live for a few minutes to a few hours. The chlorine levels between 0.1-0.3 ppm are toxic to fish. But in municipal water chlorine levels of 1.5 to 2.0 ppm so fish will not survive in it.

If my tap water is already safe to use in my tank, do I still have to dechlorinate?

Before adding fish to the tank, you need to check the chlorine level of the water with the test kit.  That will indicate if it is safe or not.

How to make tap water safe for fish without a conditioner.

Yes, it is possible to make water safe and dechlorinate water. You can use chemical-free methods such as a UV filter but it should be correctly used if you can aerate the water for 1 to 5 days it can work too. But chemicals a cheap and less time-consuming.

Read more on How to lower pH in Fresh water aquarium
Read more on Bloodworms Fish food – Best high protein fish diet 

Read more on What Causes Oily Film Aquarium Water? Problem SOLVED


Environmental Protection Agency. 2000. Wastewater Fact Sheet. Dechlorination. EPA 832-F-00-022. Washington, DC: U.S. Environmental Protection Agency.

Vitamin C To Neutralize Chlorine Hill, M. 2003. Dechlorination � Vitamin C. Welcome, NC: North Carolina Rural Water Association

Hall, L.W., Jr.; Burton, D. R.; Graves, W.C.; and Margery, S.L. 1992. Environmental Science and Technology. 15:573-78.

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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.

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