How Long Does Chlorine Stay In Water?

Your fish will not do well in the tap water due to the presence of chlorine. Trust me, chlorine present in the aquarium  can be fatal for your fish, bringing death to your fish. I know this is not what you want when you get an aquarium to raise fish. So, when will the water be free of chlorine? How long does chlorine stay in the water? How can you remove Chlorine from the water you are using in your aquarium?

Well, you need to let the water sit for at least 24 hours to dechlorinate. However, for the complete removal of chlorine, you need to let it be for 5 days or more depending on the concentration of the chlorine in the aquarium water.

Boiling, carbon filter, ascorbic acid, and air pump are some solutions for instantaneous removal of chlorine.

But I know you need more information, so I won’t leave you hanging with this piece of information only. Here is a whole article for you to know more about chlorine in water and its removal.

Let’s get started, shall we?

How Long Does Chlorine Stay In Water?

If you talking about the average time chlorine stays in the water, then we will be talking about few days. Water takes 24 hours to get dechlorinated when left undisturbed.

But for the complete evaporation of chlorine, you need to wait patiently for 5 days before adding it to the aquarium.

For the 2 ppm (parts per million) level of chlorine in 10 gallons of water, you will have to wait for 110 hours (5 days approx.) for it to evaporate completely.

If the chlorine concentration is high, then you might have to wait for a little more than usual. However, don’t risk your fish life and add tap water into the aquarium hazardously.

Test the water properly before pouring it into the aquarium. Sera Chlorine-Test and Quick and Accurate Water Test Strips – 7-1 Pool Test Kit are ideal to test chlorine.

Sometimes ‘What if’ is better than ‘Oops’. Trust me.

How Long Does It Take For Tap Water To Be Safe For Fish?

Tap water is highly chlorinated and hence quite unsafe for fish to live in. One of the common beginner’s mistakes is the way you use tap water for your new aquarium.

Don’t worry, tap water isn’t always bad but the chemical content in it can make it harsh for fish. Fish are sensitive and fragile so you need to be cautious with every step you take.

Tap water is quite safe for freshwater fish once you go through all the treatment or waiting time. But I can’t say the same thing for saltwater fish, sorry.

Chlorinated water is okay for human use until the concentration is less than 4 ppm. But this concentration of chlorine will harm the fish.

Fish needs water that is not chlorinated or has a concentration of less than 0.003 ppm. So, you can reckon what I am meaning to tell you.

Tap water is not safe for your fish until you let the water sit and aerate for 24 hours. Let the chlorine evaporate completely.

Although High Chlorine concentration might not bring death to fish immediately, it will definitely stress your fish out.

Is Tap Water Safe For Fish After 24 Hours?

Most of the time, Yes, tap water is safe for fish after you let it sit for 24 hours. The chlorine will evaporate completely after this time.

And if you want to be on the safe side and want to take no risk, let the water sit for more than 24 hours. The 48 hours of aeration will make the tap water favorable for your fish.

Tap water contains minerals and sufficient oxygen so you are on the plus side when you use it for your freshwater fish.

But remember to acclimate your fish to the tap water slowly and don’t rush the process. Or else your fish will feel the shock and stress which in turn can become fatal.

Does Leaving Water Out Remove Chlorine?

Actually, leaving the water out is the safest way to dechlorinate the water. You can’t go heating such a large amount of water every time you need to change the water.

When you leave the water for a night or two, you will see the difference yourself. The aeration causes the chlorine to evaporate completely.

But to stay on the safe side, do test the water before using it in the tank. Your patience is tested often when you decide to keep the fish tank at home.

I hope you are willing to wait for few days before you change water or introduce tap water in the fish tank for the first time.

Does Water Softener Remove Chlorine?

No, softener on its own will not remove chlorine unless you use it along with a good filter. However, it will remove magnesium, iron, and calcium present in the water.

Some of the recommended water softeners do have the feature to remove the chlorine along with other dissolved chemicals.

So, look for the water softener with granulated activated carbon. That thing works like magic when it comes to making the water of the tank softer and chemical-free.

KDF 55 Filtration Media is highly recommended water softener and you can easily purchase it from amazon.

Does Boiling The Water Remove Chlorine?

Boiling is always efficient and the fastest way to remove chlorine as well as chloramine. You see chloramine does not evaporate as easily as chlorine even when left overnight.

So, you have to find another way to remove less acidic chloramine easily. And here you have it, boiling 10 gallons of water for 8 minutes can remove around 1 ppm of chlorine.

But the latter, chloramine, asks for a little more time to evaporate even when you are boiling it. That’s why I am hoping for you to have enough patience to wait while the water boils.

More Ways To Remove Chlorine From Water

Don’t worry, if letting the water sit won’t help you solve the problem, then I have different methods in store for you.

You know I am here to help and I am determined to solve the problem. Just believe me and follow my lead.

Here are other ways to dechlorinate water when boiling seems harder and letting the water sit for 24 hours seems impossible.

Ultraviolet Light

This is the most expensive way to remove chlorine so I think you might want to skip this. You need to change the bulb more often as well.

The plus point of using UV light is, it removes both chloramine and chlorine when you treat the water with UV with wavelength 254 nanometers and radiant energy density of 600 milliliters per 1 square cm.

The time interval for dichlorination depends on the strength of UV light and the presence of organic matter in water.

Air Pump

The mechanical way to dechlorinate the water is to aerate it with the help of an air pump. You need to purchase the air pump based on the size of the tank you have.

The perfect aeration will make the chlorine evaporate faster. And hence you will have safe dechlorinated water for your fish and fish tank.

Ascorbic Acid

The neutralization of chlorine gas in the quickest way possible makes it easier for you to use water faster. Thanks to Ascorbic acid for being the easiest and most economical way to remove chlorine.

Adding 1 spoon of ascorbic acid for each gallon of water and stirring it gently will suffice. You will have dechlorinated water in no time with no depletion in the oxygen concentration.

Carbon Filter

The activated carbon present in the aquarium filter will not only remove organic compounds but also remove chloramine and chlorine efficiently.

Test the water pH level before using an activated carbon filter and make sure it is safe for use.

Frequently Asked Questions

Here are the answers to some FAQs you might be wondering about. Hope this helps.

How Do You Remove Chlorine From Tap Water?

There are few ways to remove chlorine and I will list them for you:

  1. Treating with water distillers
  2. Neutralization of water with chemicals
  3. Water Filtration
  4. Use of activated carbon in the filter
  5. Boiling the water
  6. Evaporation
  7. Use Ultraviolet Light
  8. Use Reverse Osmosis


To sum up, I know you want everything best for your fish. So, if you are planning to use tap water in the aquarium, make sure you remove all the chlorine and chlorine essence from it. Let the water sit for few days, use ultraviolet light, boil it, use ascorbic acid, use a carbon filter, or use an air pump, do anything you prefer. But do not risk the health of your fish just because you are impatient. Fish are sensitive and fragile, treat them with love and care.

Just follow the instructions carefully when it comes to petting a fish in a home aquarium.

Good Luck!!

Happy Fishkeeping!!!

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