Dechlorinate Tap Water for Aquariums Without Chemicals

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If you own a fish tank, you surely thought about using tap water in it. If that’s the case, there is a big problem you need to consider: the chlorine that’s in it.

Does Tap Water Contain Chlorine?

Tap water does contain chloride, most of the time quite a lot of it. Why? There’s a good reason why chlorine is added in tap water: it kills all the disease-causing bacteria, that might be present in the water supplies. Actually, chlorine is among the most efficient disinfectants used in public waters.

Because of its wide use in public waters, a natural question arises:

Is Chlorine Harmful for Fish?

The short answer is YES, chlorine is quite harmful for fish. But why and how?

Chlorine can cause burns on a fish’s body. The most susceptible area to burns on a fish, is where the gills are placed. These can get burned very quickly, when the water contains too much chlorine.

Also, the burns will lead to other problems. They can cause all kinds of diseases, and your fish can even die from burns caused by chlorine. Something interesting and worth knowing, is that chlorine will be absorbed into the bloodstream of the fish, thus leading to burns all over its body.

Another negative effect of chlorine on fish, is stress. If the chlorine is not enough to kill the fish, only to hurt them, it will stress them out very much. After all, they could be in constant pain due to the chlorine concentrate.

How do you know if your fish are stressed, because of this substance? In most cases, they start to swim around quickly and gasp all over the tank, for no apparent reason. There have been many occasions, when fish even jumped out of the tank, due to large chlorine quantity in the aquarium.

I think you get the point: chlorine is really dangerous for fish, no matter which species you have in your tank. If that’s the case, is tap water good for your fish? Can you use it?

Can You Use Tap Water for Fish?

If you don’t get rid of the chlorine in the water, no, you can’t use tap water. If you do that, your fish will begin behaving like I described above, and they will start showing signs of stress and possibly even die because of a larger concentration of chlorine.

However, that doesn’t mean you cannot use tap water at all for your fish. If you dechlorinate it properly, you can use it and it is safe for your fish. The easiest method would be to use a dechlorinator or water conditioner to instantly remove chlorine from the tap water. However, if you don’t want to use any of the available water conditioner chemicals in your aquarium, there are other ways to remove chlorine.

Let’s see 5 ways that you can use to dechlorinate the water, without the need to use chemicals:

1. Let it Sit for 24 Hours

This is the simplest method, to get rid of the chlorine in the water. Just get some tap water in a vessel, then leave it like that for at least 24 hours. What happens during this time?

Most of the chlorine will simply evaporate from the water. Yes, you’ve read that right.

Usually, tap water contains a normal dose of chlorine, which can evaporate in around a day, if you leave it standing in a vessel. However, if you want a quicker process, check out the other 4 methods I’m going to mention right below.

2. Use a UV Light

A UV light is also a great tool that can help you dechlorinate some tap water. Why? If you put a UV light beside some tap water, it will neutralize the chlorine that’s inside it. It’s that simple.

The time period in which this can happen, depends mostly on the volume of water you try to clean from chlorine. It’s best if you do it in steps of 10 gallons at a time. This way, you can make sure, the chlorine really leaves the water.

A UV sterilizer is a device that is used in conjunction with water filter in fish tanks. Such a device can clean the water from many things, chlorine as well.

To make the most out of this method, it’s advised to use it while you leave the water outside for 24 hours. If you put water in a vessel, and leave it there for 24 hours and you also add a UV light upon it, you can be sure there will be no chlorine in it when you’re done.

3. Boil the Tap Water and Let it Cool

This is actually the most effective way, used to dechlorinate tap water. That’s because it’s quick and easy to manage. Literally anyone can do it. All you have to do is boil the water for around 8 to 10 minutes, and the chlorine will evaporate from it.

This amount of time is best for around 10 gallons of water. If you boil more at one time, you might need to raise these number to even 15 or 20 minutes.

However, when you stop the boiling process, don’t forget to let it cool down. Otherwise, your fish can’t live in that environment.

4. Pre-Filter with Reverse Osmosis or Carbon Filter

Reverse Osmosis is a water filtration method, that is done by many people worldwide, not only for aquarium purposes, but to obtain drinking water as well. Since that’s the case, it’s to be expected, that Reverse Osmosis will remove chlorine from the water as well.

The system is simple and straightforward: a pump is used to pressure the water through a semipermeable membrane. During this process, all the impurities remain on the membrane. For instance, besides chlorine, the Reverse Osmosis filtration is used to remove salt from water too.

A Carbon Filter is similar to the one above. The difference is, that the water is pushed using a pump through a mass of carbon. This carbon will physically absorb all kinds of chemicals and substances that are dangerous to consume.

Chlorine is among those chemicals that get absorbed by the carbon layer. There are 2 types of carbon filtration systems. The difference comes in the carbon itself: on version has granular layer of carbon, when the other is made of a block of carbon. However, the result is all the same: dechlorinated tap water.

5. Use Vitamin C

Yes, you can use vitamin C, to dechlorinate tap water. Actually, this is one of the most popular methods, because it’s very simple to do, just like some of the other methods from above.

All you need to do, is add vitamin C to your tap water, and it will neutralize the chlorine in it. The downside is that you must buy vitamin C tablets or maybe powder, which you can use against the chlorine. Here is a complete study on how vitamin C will neutralize chlorine in water.

Even so, this method is quite efficient. People use it to dechlorinate even pools, hot tubs and baths, not just small amounts of tap water. So, it will surely do the job, like you wouldn’t even expect it.

These were the 5 best ways to dechlorinate tap water, without using any kind of chemicals.

Dechlorinate Tap Water with Chemicals

Now, let’s see a little about this technique as well. Chemical dechlorination consists in using different sorts of chemical substances, to filter the water, and get rid of chlorine. These are called water conditioners. They have the ability to quickly remove all the chlorine from the water in an efficient way.

If that’s the case, then what’s the problem with it?

These conditioners contain all sorts of chemicals, that in most cases affect your fish in a negative way. They can lead to multiple health problems and even diseases inside your tank.

Because of this, when you want to dechlorinate some tap water, it’s best if you go the natural route, instead of using water conditioners.

This way, you’ll make sure your fish will live a log and healthy life in your aquarium, without any issues from the water they live in.


All in all, chlorine is a substance that needs to be removed from any types of tap water, if you plan to use that in your aquarium.

This article helped you learn about 5 efficient methods, that work for most people when dechlorinating tap water:

  1. Let it rest for 24 hours
  2. Use a UV light to sterilize it
  3. Boil the water and wait for it to cool down (most efficient and simple way)
  4. Filter by Reverse Osmosis or Carbon Filtering
  5. Use vitamin C in ta water

I personally recommend the first and last methods for beginner aquarium enthusiasts. These require no prior knowledge or any sort of research to be made, before applying.

Also, both of these are quite efficient, and have no negative effect on your water life. However, the other first methods are just as good, they only need to wait some time to work well.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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