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Is Tap Water Safe for Fish? (6 Ways to Make It Safe for Aquarium)

Have you ever wondered if tap water is safe for fish? It is, after all, the most affordable and accessible water out there.

Keep reading to find out if it’s the best fit for you and your fin-icky friend!

Tap water is safe to use in your fish tank so long as you take certain safety measures first, such as dechlorination and removing all other harmful minerals that your water may contain that could be toxic to your fish.

Keep reading to find out how to make tap water safe for your fish.

How to Dechlorinate Water

tap water for aquarium

Chlorine is the main reason why tap water is unsafe for fish.

Most tap water is treated to make it safe for drinking. Usually, it will contain chlorine and chloramine (a combination of chlorine and ammonia). Both of these are very harmful to fish. 

But don’t worry, I’ve compiled a list of ways for you to make sure your tap water is chlorine free before you ever put your fish in it

1. Simply Let the water Sit

Let the water you intend to use sit out for no less than 24 hours. During this time, most of the chlorine will evaporate into the air. 

After 24 hours, it should be safe enough for your fish to live in. 

The more water you have, the longer it will take to evaporate the chlorine, so make sure to only have the water you are going to use sit out. 

Also, make sure no insects or debris get into the water as well. 

This method doesn’t work for removing chloramine.

2. Use Vitamin C

Vitamin C (Ascorbic Acid) is a common method used to dechlorinate water, as it effectively neutralizes chlorine without affecting the pH level of the water.

Vitamin C is sold in the form of dissolvable tablets or as a powder. Follow the instructions on either, to dechlorinate tap water. 

This method usually takes around 5 minutes to work.

3. Use a Water Conditioner or Dechlorinator

Water conditioners and dechlorinators do basically the same thing. They are used in fish tanks to eliminate chlorine and sometimes chloramine. 

Be careful which ones you get, as some can have negative effects on your fish. 

I recommend Seachem Prime water conditioner. It's specially made for aquariums and it works! Check out its latest price at Amazon here

It’s safe to dechlorinate the water you intend to add to your tank 5 to 10 minutes before adding it. You can also add the dechlorinator directly into the tank with your fish before adding new water. 

Always read the instructions on the container to know exactly how much to use. However, it’s generally recommended that you use a dose big enough to cover the volume of your entire tank.

4. Boil Your Water

Yes, boiling water does, in fact, dechlorinate it. Chlorine, when in its gaseous form, weighs less than air. This is why it can evaporate out all by itself by simply leaving it to sit out for a day. Boiling significantly speeds up this process. 

However, boiling may not be the most efficient way to deal with chloramine, as it can take much longer to boil that out of water.

Most cities put chloramine in drinking water, but the only way to know for sure is if you test your water. It is possible to boil chloramine out; it will just take quite a bit longer. 

Boiling water for at least 15 minutes should be long enough to evaporate the chlorine.

If you are boiling more than 10 gallons, you should boil for longer, more like half an hour or so. The times are less known for chloramine, but I would say boil for no less than 2 hours.

Be sure to let the water cool before putting it in your fish tank.

5. Use UltraViolets

UltraViolet lights are very effective in eliminating chloramine and chlorine from tap water, as well as many other harmful bacteria and contaminants. Just make sure you get one powerful enough to eliminate both. 

Your UV light should have a 254-nanometer wavelength and a radiant density of 600 milliliters.

If you want to dechlorinate water before adding it to already purified fish water, you can put a UV light next to your container of water and angle the light above the water. 

Or, you can add water directly to your fish tank as long as you have a UV lamp installed in your fish tank beforehand. They’re inexpensive and easy to install. 

In fact, most fish tanks come with them already preinstalled. Make sure you allow the water some time to dechlorinate before adding your fish. 

Waiting about 10 minutes should give the UVs enough time to purify the water. 

6. A Water Filter

The most efficient and common type of filter used for dechlorination is an activated carbon filter. These are often included in most fish tank filtration systems.

Carbon filters work because the activated carbon inside them absorbs many harmful chemicals and minerals that could harm your fish. This includes both chlorine and chloramine.

There are three ways you can go about using this method, although it can be more expensive than the others.

You can have a separate tank specifically for dechlorinating water and have a carbon filter installed in it. Once that water is dechlorinated, you can add it to your fish tank with your fish. 

Or you could add a filtration system to your water faucet or directly in your plumbing so that all your water is filtered immediately once it exits your faucet. 

Additionally, if you are starting a new tank and don’t have any fish yet, you can simply put the water into your tank with a carbon filter. Once it’s done filtering, you can add your fish. 

What If I Don’t Dechlorinate Water?

I’ve told you that chlorine is bad for fish, but I haven’t told you why. 

You’ll first notice burns near and on its gills when a fish is exposed to chlorine. It starts on the gills, the most sensitive part of a fish’s body. 

Eventually, the fish will absorb the chlorine into its bloodstream, and the burns will start to appear all over its body. These burns can kill your fish or cause other terrible illnesses. 

Chlorine can also cause cell death in fish by reacting to organic matter and tissues. Again, the gills are exposed first, which can lead to breathing difficulties, asphyxiation, and death. 

Over-exposure to chlorine can also affect your fish mentally. Stress plays a big part in this. 

One of the main reasons fish become stressed in this situation is pain and lack of breathability. 

You may notice erratic swimming, gasping at the surface or random places, difficulty swimming, stiltedness, “jumping” out of the tank, and often sudden death. These are all signs the fish is being negatively affected by the chlorine. 

Some physical signs of chlorine exposure are redness all over the body, paleness, or being covered in a mucous-like membrane. 

How To Treat Your Fish For Chlorine Poisoning

Although fish usually die when exposed to too much chlorine, there are some ways it can be helped if you act quickly. 

You must neutralize the chlorinated water immediately if your fish will have any chance of survival. 

Unless you have another container with chlorine-free water available to transport your fish into, in which case you should remove your fish from the contaminated water and immediately put it into the clean water. 

There are many quick-working dechlorinators on the market, so having those handy at all times would help you prepare for emergencies like this one. 

Plus, many also eliminate other harmful contaminants that could wind up in your fish tank water. 

I recommend Seachem Prime water conditioner. It's specially made for aquariums and it works! Check out its latest price at Amazon here

If your fish is exposed for even a minute too long, the damage will likely be permanent, and it may not be able to heal from it. All you can do is wait, keep it as healthy as possible, and hope it heals.

How to Care for Fish Suffering From Ammonia Poisoning

Unfortunately, most fish will die if they are exposed to chlorine. But some will survive!

You’ll need to take good care of the survivors to give them the best chance to heal.

Feed the fish high-quality food

If the survivor fish is eating food, feed them compatible, high-quality live and frozen foods. 

Keep them in a separate tank

You don’t want the fish suffering from chlorine poisoning to be picked on by other fish. That’s why, if you can, you should keep the fish in a separate tank.

Just make sure that the fish tank you’re keeping them in is already cycled. And the water parameters are within the ideal range that the fish need. 

Keep the water quality high

As the survivor fish are already suffering from chlorine poisoning, their immunity is already very low. 

So at this point, you need to make sure to keep the water quality of your fish tank as high as possible to give them the best chance to heal. 

So you’ll need to: 

  • Do water changes more frequently to keep the ammonia levels low
  • Remove uneaten food from the water
  • Maintain the water parameters of the tank within the ideal range


What Is The Best Water For Fish Tanks?

Deionized water remains one of the best types of water for fish tanks and aquariums because it is free from chemical and mineral contaminants. So your fish will not be exposed to the most harmful contaminants. However, deionization isn’t effective at removing bacteria. 

Besides, deionized water also strips away the good properties of water, so you will still need to adjust the water before it is ready for fish.

How Often Should You Change Your Fish Tank’s Water?

Generally, you should change your fish tank water on a weekly basis. And each time, you should change anywhere between 10% to 50% of your fish tank water. Exactly how much water you should change depends on the nitrate levels that build up in your tank throughout the week. 


Tap water can be safe for fish if you dechlorinate it and remove other harmful toxins from it before adding it to your tank.

If not, your fish would likely die. 

Be sure you thoroughly go through at least one of the ways I’ve mentioned in the article for dechlorinating tap water before adding it to your tank to make it safe for fish. 

Happy fishkeeping!

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Prathmesh Gawai
He is the main author and editor at Aquagoodness.com. And he loves to share helpful information on aquarium and/or fishkeeping hobby. Prathmesh has over five years of aquarium and/or fishkeeping experience. Currently, he has a Betta fish tank. He has written hundreds of articles on various aquarium fish species and on fish tank maintenance over the last five years. Connect with him on YouTube here. Learn more about him here.

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