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How To Safely Dechlorinate Water For Fish Without Chemicals: 5 Step Process

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By Lindsey Stanton


If you are getting ready to put fish in the tank, of course, you are going to need to add water first. Your fish cannot live without water, so this is not a choice! However, some issues arise from the need to fill your aquarium with water, with the chlorine contained in your tap water being the biggest issue.

Today we want to talk about how to dechlorinate water for fish without chemicals, water for your fish tank can be dechlorinated in several ways. Boiling the water, letting it sit for a day, using specialized filters, and using UV sterilizers are all good options here.

However, do keep in mind that most tap water contains both chlorine and chloramine, and chloramine is much harder to deal with but just as harmful to your fish as chlorine, something we will touch on in a little bit.

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Does My Tap Water Contain Chlorine?

kitchen sink tap water
Image Credit to: Unsplash

The long story made short here is that yes, your tap water will usually always contain chlorine. This is especially the case if you live somewhere you are getting your water from the city or municipality. Drinking water you pump out of your tap usually always contains chlorine.

It is added into the water to kill dangerous bacteria, viruses, and microorganisms which can be harmful to human health when ingested. So, yes, when it comes to humans drinking chlorinated tap water, it is perfectly safe.

However, the same cannot be said for fish, not in the least. The moral of the story here is that you cannot use plain and untreated tap water for your fish tank due to its chlorine content.

Is Chlorine Harmful to Fish?

Yes, the chlorine found in tap water and other water sources contains chlorine, and usually a whole lot of it, and yes, it is harmful to fish. For one, it will burn their eyes, mouths, and gills.

It will cause a fish a whole lot of pain if it is forced to be in water that has chlorine in it. Even worse than that, because the fish lives in that water, drinks that water, and breathes oxygen by filtering it out of the water, this chlorine then makes its way into the fish’s body. This will then quickly result in permanent and long-lasting damage, more or less just the complete failure of all bodily organs combined with a whole lot of pain. So, not only is chlorine harmful to fish, but it will downright kill them every single time.

The point to take away here is that you can absolutely not use any kind of chlorinated water to house your fish.

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The 5 Steps to Dechlorinate Water Naturally

The whole point here is to help you dechlorinate water naturally and effectively without the use of harsh chemicals, such as are found in water conditions.

Well, there are a variety of methods that you can use in order to dechlorinate water naturally, so let’s talk about each of them in some detail.

1. Let It Sit

One of the easiest ways to dechlorinate water naturally is to let it sit for a while. So, how long does water need to sit to dechlorinate? Well, this depends on how much water you are looking to treat for chlorine, how much chlorine the water contains, and how much exposure to sunlight it gets.

Generally speaking, tap water needs to sit out in the open for about 24 hours in order for all of the chlorine to dissipate. If you have a wide container and there is lots of exposure to sunlight, it could take 20 hours or less, but if you have a narrow container with no sunlight hitting it, it might take well over 24 hours. For this, it is best if you let it sit for longer rather than rush things, just to be sure.

However, do keep in mind that a lot of tap water contains both chlorine and chloramine, and chloramine is not air soluble, so if your water contains chloramine too, simply letting it sit will not get the job done and will require a more intensive solution.

2. Using Ultraviolet Light

aquarium bright lights
Image Credit to: Sergio Bertino, Shutterstock

Another natural way to dechlorinate water for fish is to use a UV sterilizer. If you have a reef or saltwater tank, you might already have a UV sterilizer. If you do not, they are not too expensive to buy, and they work wonders in terms of naturally dechlorinating water.

These work by bombarding the water with UV rays, which due to some super scientific reasons, will treat the water and kill the chlorine. For some specs, your UV light should be putting out light at the 254-nanometer wavelength with a radiant density of 600 milliliters.

As long as your UV light can work with these parameters, you don’t even really need to know what those specs actually mean. These sterilizers are really effective at dechlorinating water for fish, and can then be put to use for the fish tank itself. What is also important to note here is that UV sterilization will remove chlorine and chloramine.

Chloramine cannot be removed from the water by just letting it sit, so this is important to note.

If you need help getting the water quality in your aquarium just right for your goldfish family, or just want to learn more on the subject (and more!), we recommend that you check out our best-selling book, The Truth About Goldfish.

The Truth About Goldfish New Edition

It covers everything from water conditioners to nitrates/nitrites to tank maintenance and full access to our essential fishkeeping medicine cabinet!

3. Boil the Water

One of the easiest ways to remove chlorine from water for fish the natural way is to boil the water. This is very easy to do, it is effective and safe, and it won’t cost you much either.

The boiling heat and the aeration created when boiling water is more than enough to remove chlorine from the water. Simply boil the water you wish to put in the fish tank for around 20 minutes to remove all chlorine. This has the added benefit of also removing chloramine from the water, which is very important to note. Sure, you might have to boil a few pots depending on how much water you need for the fish tank, but it is safe and fast.

Just remember to let the water cool down before putting it in the aquarium!

4. Carbon Filter or Reverse Osmosis Filter

Now, you do also have some slightly more expensive options for dechlorinating water naturally. For one, you can go with a good old carbon filter. You might have noticed that carbon filters, with activated carbon, are also used in fish tank filters.

The activated carbon has the power to remove chlorine, chloramine, and a host of other compounds from water, which is why it is used for fish tank filter media.

Well, it also does a good job of removing chlorine and chloramine from the water before you put it in the fish tank. There are some carbon filters that can be used after the water comes out of your faucet, and there are some that can be installed directly in the plumbing, so all of your water is always carbon-filtered.

Another option here is the reverse osmosis filter, which works just fine, but beware that these can only be installed directly in your plumbing, they are expensive, and they produce a lot of wastewater too.

Hands comparing old and new activated carbon material of a fish tank filter
Image Credit to: Ladanifer, Shutterstock

5. Vitamin C Treatment

The other natural method for dechlorinating water for your fish tank is to use vitamin C, which when used for water treatment like this comes in the form of ascorbic acid. Here, simply add one teaspoon of ascorbic acid to every gallon of water you plan on putting in the fish tank.

This stuff quickly neutralizes both chlorine and chloramine in a very short amount of time, and when used for water treatment, is perfectly safe for fish to swim in.

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Chlorine vs Chloramine

So far we have been talking about chlorine and chloramine. What you need to know here is that depending on where you live, your tap water might only contain chlorine, or it could also contain chloramine. The only way you will find out what the water contains where you live is by doing some research into the water treatment practices of your water supplier.

The point here is that chlorine is much easier to deal with as it can dissipate into the air. However, chloramine does not dissipate into the air, and no matter how long you let water sit, if it has chloramine in it, it won’t be going anywhere.

Simply letting water sit is not enough to deal with chloramine, so you will have to put one of the other natural water dechlorination methods to use which we have talked about above.

Best Water to Use for Aquariums

Yes, you can use tap water and simply treat it for chlorine and chloramine. However, when it comes down to it, if you have a bit of cash to spend, some simple bottled water is usually the best way to go for fish tanks.

However, you can also buy specially treated water for aquariums at some pet stores, which is another way to go.

Dechlorinating Water with Chemicals

There are special chemicals out there known as water conditioners that have the ability to quickly and effectively remove chlorine from water so you can use it for your fish tank (we have covered the 7 best ones here).

However, these conditioners in themselves contain various chemicals and elements that are not exactly healthy for fish to live in.

Therefore, when it comes to dechlorinating water, while you can go the chemical route, it is best if you do it naturally in order to provide your fish with water that is as healthy to live in as humanly possible.

yellow tang swimming under water
Image Credit to: Piqsels

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There we are folks, all of the natural ways to dechlorinate water for your fish tank, all without the use of any chemicals. Remember guys, if you put your fish in normal tap water that contains either chlorine and/or chloramine, your fish is going to be in serious trouble, so never forget to treat your tap water for these substances before pouring it into your aquarium.

Featured Image Credit to: Kaori, Pixabay

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