Dechlorinate your Aquarium Water for Fish and Plants

Because the water quality is crucial to our fish’s health, dechlorinating your water before putting it in your tank is a must. I always dechlorinate my water before adding it back in my freshwater aquariums.

Should you dechlorinate the water that you add in your aquarium? Yes, especially when the water quality in your location has a high amount of chlorine in it. We do this because the concentration of chlorine in tap water hurts our fish and invertebrates, up until the point that it might kill them.

You do however have to make sure you are using a product that is not damaging your filter and the product should not neglect chloramine, as a lot of tap water is also treated with this. Also, there is a method where you can use an air stone to remove the chlorine in a bucket overnight, but that only works when your water is not treated with chloramine.

How do you know if you should treat your water

Most municipal tap water is treated with chlorine, chloramine or both. Chlorine used to be the standard desinfectant for our tap water for a long time, with the goal to control all kind of microorganisms and bacteria in our water.

Nowadays a lot of municipalities have switched to chloramine, which is created by adding ammonia to drinking water that contains chlorine. It is more stable compared to chlorine. Chlorine is volatile and chloramine is not.

So how do you know if your water contains a lot of chlorine and chloramine? If you do not know, ask your local fish store. They will definitely know all about the quality of your local tap water. A lot of the times you can even take some tap water to the store and they can test it for you.

What exactly is a dechlorinator

The municipality will have added chlorine and chloramine to your tap water for very good reasons. It kills bacteria that are unwanted in our drinking water.

The dosage of chlorine and chloramine that is used in the water is not harmful to human, but also not for a lot of other animals like cattle, dogs, cats, horses etc. The problem is that it is harmful to fish and invertebrates (snails, shrimp and lobsters) and therefore should be removed before we add the water to our tank.

What a dechlorinator does is essentially neutralizing the harmful substances chlorine and chloramine. It makes sure that the water after treatment is safe for our fish and the beneficial bacteria in our aquarium. We will talk about different kind of dechlorinators in a bit, but ideally both substances are neutralized.

When to use a dechlorinator

Almost all fish keepers use tap water as their main source of water for their tanks. There are exceptions, because some people have excess to a well or buy their water at their local fish store.

If you fill up your aquarium for the very first time, fill up the part of the tank that has evaporated or do a water change, you will have to prepare the water for your fish. In all these cases you add new water that has been treated with chlorine and chloramine to your tank.

Adding dechlorinator is relatively straightforward, but you have to make sure that you follow the instructions on the packaging. Always use the right doses for the amount of water that you are adding to your fish tank.

Are all dechlorinators equally good?

You can buy dechlorinators at almost any fish or pet store, and frankly they are not even that expensive. But will they all do their job the way we want them to? Not all of them do, but that is not problem if you know what to look for.

We have just learn about the difference between chlorine and chloramine. Chlorine is volatile, whereas chloramine is more stable. But what has this to do with different kind of dechlorinators? Well: all dechlorinators remove chlorine, but not all of them remove chloramine.

Make sure when you are buying a dechlorinator, you read on the packaging if it says that it removes both chlorine and chloramine. If it does not explicitly state that is neutralizes chloramine there is a chance that is only neutralizes chlorine.

The really basic dechlorinators only target chlorine, where most of them also neutralize chloramine. There are even more “fancy” dechlorinators that have added substances like stress reliever, skin tonics, vitamin E or aloe extract. These extras will add to the price of the dechlorinator and are generally not necessary.

What dechlorinator should you get?

Now the important part, which dechlorinator should you buy to make sure that your tap water is safe for your fish?

Keeping everything we just discussed in mind, the aquarium dechlorinator that I highly recommend is the one by the brand Seachem. You can check it out here on Amazon.

You will not regret buying this one, it is affordable and will make your water safe for your fish to live in.

Can chlorine damage your filter

Chlorine is used in our water to disinfect it and kill a lot of bacteria. This is great because a lot of the times we do not want those bacteria finding a way into our food, drinking water and our fish tank.

The chlorine however can also damage the beneficial bacteria that have been building up in the filter media (but also on the substrate, glass and ornaments) of our tank. These bacteria are crucial in breaking down the ammonia and nitrite into less harmful nitrate.

This is something we definitely do not want, as the beneficial bacteria are more than welcome in our tank. We need them!

Do not fully rely on evaporation

A lot of people that do not use a water conditioner rely of the volatility of chlorine. They fill up a bucket with water that they want to use for a water change and leave it for a night so all the chlorine will evaporate, sometimes even adding an air stone.

Is this enough to prepare your water for your tank. No, relying on evaporation will remove the chlorine, but the chloramine that is in the water will not evaporate. It will therefore still be in the water when you add it to your tank. Because chloramine is more stable that chlorine (a big reason why it is nowadays used in the first place) it will not leave the water as easily as chlorine.

I want to add that you should ask your local fish store if your water is treated with chloramine. If they are certain that it is not, this method is a good way to remove the chlorine. But only chlorine.

Related Questions

How do I see if my fish are suffering from too much chlorine/chloramine in the water? This is a relevant question, and most of the time happens to beginner fish owners that have added tap water to their tank that contains too much chlorine. Fish that are suffering from chlorine poisoning hover near the top and can be gasping for air. They can also develop red areas on their skin and it may seem like the fish is covered in a mucus layer.

Can I use a dechlorinator when the new water is already in the tank? Yes, but this might get complex. If you have not been using a dechlorinator before and you want to start using it, you should add the recommended dosage for the amount of water in your tank.
If you do a water change first and have always been using a dechlorinator, you can add the recommended dosage for the amount of water that you have added to your aquarium.

If my tap water is already safe to use in my tank, do I still have to dechlorinate? No, not necessarily. Before you decide that you do not need a dechlorinator, make sure you go to your local fish store and ask them what they think of the tap water. If they say it is safe to not use a water conditioner product, you are good to go. I need to stress that the fish stores most of the times do intent to sell you products, even when they are not critical for your hobby.

Bart Sprenkels

I have been keeping multiple aquariums since I was 18 years old. Just like many of you, I started with two goldfish but quickly learned they were not suitable for aquariums. Later, I switched to a tropical community tank and I also have two pet musk-turtles in a bigger aquarium. You can read more about me here.

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