Can you put a fish water conditioner in the tank? (2023)

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As an aquarist, I have repeatedly treated the water for my fish. Of course, I found water purifiers to be the most convenient. However, I wasn't sure if I should be doing the rinse while the fish are in the tank. After extensive research, I'm ready to share all the lessons I've learned.

You can use a water conditioner while the fish are in the tank, as water conditioners are generally safe to use. However, it is best to take the fish out for at least 15 minutes in small, crowded tanks. This allows the conditioner to spread evenly throughout the aquarium.

As we go along, I'll share with you some tricks on how to properly condition your aquarium with an aquarium conditioner. I'll also show you how to use boiled water for the same purpose. This trick and a few others will allow you to condition your water even after your current conditioner has run out.

Can you put a water conditioner in the fish tank?

Can you put a fish water conditioner in the tank? (1)

Most aquarists know the importance of regular water changes. This is the only way to keep the pool free of toxins and pollutants. However, when you introduce new water into an aquarium through a water change, you also run the risk of adding toxins and contaminants.

This is where water purifiers come into play. You can use them to eliminate ammonia, chlorine, chloramine and any metals that could threaten your fish. However, it is less clear how you should care for your fish when using these products.

Two main reasons lead to such questions. First, because water conditioners are chemicals, some people worry that the products will harm their fish. Therefore, they believe that the fish must be removed from the tank before conditioning the water.

Second, because water conditioners are used to remove toxins from new water, some aquarists worry that the toxins will cause irreversible damage to their fish before the water conditioners can remove them.

These concerns seem justified but are mostly unfounded for two reasons:

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  • Most water conditioners are safe and will not harm fish. A water conditioner dangerous for fish will warn you, so I recommend reading the instructions on the package. However, most water conditioners guarantee the safety of your fish.
  • The best water conditioners such asAPI Water Conditioner (link to Amazon), work immediately.[1]For this reason, some people prepare new water and pour it into the tank at the same time. You know these products work in minutes. Conditioners quickly neutralize toxins before they can harm your fish.

So you don't have to take the fish out of the tank to add the water conditioner.However, you are free to take whatever precautions you feel are necessary to protect your fish. This includes pulling them out of the water before adding conditioner.

How long after adding a water conditioner can I add fish?

Fish can be introduced into the tank fifteen minutes after treating the water with a conditioner. This is especially true for old tanks that don't require cycling. However, fish can usually be added to the tank immediately after using a conditioner, or even remain in the tank throughout the process.

It is worth repeating that it is not necessary to remove the fish to condition the water. That said, some people prefer to keep their fish in a separate tank while changing and treating the water. Finally, the waiting time depends on your situation:

old tanks

In most cases, it shouldn't take more than 15 minutes for the conditioner to remove toxins from the new water. At this point, you can release the fish knowing full well that the water is safe. This assumes you have an older tank that has already been assembled.

new tanks

If your tank is new, you should still treat your tap water with water conditioners. In this case, however, a product that removes the chlorine and leaves the ammonia for the bacteria to consume is enough.[2]

After treating the water, you have to wait a month for the tank to start working again. Water conditioners do not change anything here and cannot speed up the process. Each new tank requires a cycle before fish is added.

Can water purifiers kill fish?

Water conditioners can kill fish, especially in concentrations greater than five times the recommended dose. This often happens in small, crowded tanks or when the product is mishandled. In general, though, water conditions are considered safe for fish.

As mentioned earlier, water conditioners are safe.[3]That's why you can add them to a tank without removing the fish. Of course, it depends on the crowd. Some conditioners need to be added in small amounts because they are so concentrated. Others need to be added in larger amounts as they are more dilute.

(Video) Add Fish to New Tank on Day 1 - (It Works Every Time)

Smaller tanks are also tricky as you can easily add too much conditioner. But even in these cases, the best brands claim that you can add two, three or even five times the recommended dose of conditioner and it won't harm the fish.[4] So even in the event of an accident or spill, the chances of a water conditioner killing your fish are slim.

Why is a water conditioner necessary for my fish?

Water conditioners are commercial products that aquarists add to aquariums to remove toxins. The first great water conditioner was sodium thiosulphate.[5]It was not the only product designed to combat chlorine, although it was the first to show truly revolutionary results without harming the fish.

Sodium thiosulfate can eliminate chlorine immediately. However, when chloramine was introduced, aquarists found that sodium thiosulfate was no longer sufficient. It could still remove chlorine, but it left ammonia behind. Today, the market is full of water conditioners that can fight chloramine. They remove chlorine and then neutralize ammonia.

Water conditioners are necessary as most aquarists get their water from a faucet. Tap water is easily accessible, although it is also treated with chemicals to make it safe for human consumption.

Initially, tap water was only treated with chlorine. But that didn't make him any less dangerous. Chlorine is a toxic substance that must be maintained at levels of 0.003 ppm or less in an aquarium.[6]Traces stress fish, and concentrations as low as 0.2 ppm kill even aquarium fish.

Despite the danger it posed, chlorine wasn't necessarily a problem for fish experts because it eventually evaporated. But then it became quite common for governments to treat tap water with chloramine, a combination of chlorine and ammonia. And unlike chlorine, chloramine doesn't just evaporate.

How to condition water for fish?

Purifying water for fish involves the following steps:

  1. Boil the water for at least 8 minutes.
  2. Leave the water for about 24 hours.
  3. Place a water conditioner in a separate container.
  4. Let the fish rest in this container for a while before adding them to the aquarium.
  5. Use a biological filter that contains sodium thiosulphate in the community aquarium.

If you are new to the aquarium hobby, here are some things to keep in mind when preparing water for your fish. These steps will ensure that your fish are not unnecessarily exposed to the ammonia and chlorine found in tap water:

1. Ways to condition aquarium water without conditioners

Although water purifiers make it easier to remove toxins, there are ways to purify your water without using these products. For example:

(Video) Aqua Care Water Conditioner Review: Paano Gamitin, Water Change Routine And Benefits For Aquarium


You can remove chlorine by letting the water stand. The substance is unstable. Therefore, given enough time, it will eventually disintegrate and evaporate from the water. In many cases, letting the water sit for 24 hours will rid it of dangerous levels of chlorine.

You can speed up this process by adding filters and air stones to improve ventilation and circulation. However, as mentioned earlier, this does not work with chloramine. Unfortunately, the toxin is more stable than chlorine.


If you don't want to wait, try boiling water. It can take eight minutes to remove chlorine from a 10-gallon tank.[7]Boiling also works with chloramine, although it takes longer. For example, while you can boil 1 ppm of chlorine from 10 gallons in 4 minutes, it takes 65 minutes to remove a similar amount of chloramine.

Biological Filter

This method involves the use of a dechlorinating agent such as sodium thiosulfate. Place the dechlorinator in a container of water to remove the chlorine. After that, you can connect the container to a biofilter, which converts the remaining ammonia into nitrate.

However, the downside of these methods is that it takes a while to get results. That's why people prefer water conditioners. I personally prefer using conditioners and am not too worried about them harming my fish.

2. Conditioning aquariums with a water conditioner

You can use one of two methods to treat your water with water conditioners:


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If you normally use a separate container to add water to your aquarium, treat the water in the container before adding it. Take a conditioner, fill the container with water, measure the conditioner and add it to the new water in the container. It would be helpful if you also took a moment to spin it around before dumping it in the aquarium.


If you do a water change with a hose, you can already add the water conditioner to the aquarium while the new water is entering the aquarium. With the tank option, you only need enough conditioner to treat the water in the tank.

With the hose option, you need to determine the correct amount of conditioner needed to treat the entire aquarium. After measuring out the conditioner, slowly drip it into the water as it flows into the aquarium.[8]

Anyway, if you're unsure, remember that water conditioners have instructions to tell you the right amount. I also recommend watching some Youtube videos that give you a visual understanding.

Water conditioners must be used when adding water to the tank. So with every water change. Basically, any new water needs to be conditioned before adding it to the aquarium.

What types of water purifiers should I consider?

There are three main types of water conditions to choose from, namely:[9]

  • Entchlorungsmittel– As the name suggests, these conditioners remove chlorine. You will ignore ammonia and heavy metals. People don't use them as often because they prefer products that can attack both chlorine and ammonia.
  • chloramine neutralizers– These products also have apt names. They neutralize the chloramine in the water by removing the chlorine and then binding to the ammonia molecules, creating ammonia, which does not kill the fish.
  • Complete Conditioner– These products can do a little bit of everything. They attack chlorine and ammonia while removing heavy metals and copper. You can also count on them to buffer the pH and protect the mucus membranes that fish use to fight infection.

Before treating your water, you need to identify the types of conditioners you will be using.If you want to save yourself the hassle, I recommend youAPI TAP Water Conditioner (Link para Amazon).I've never had any issues with this product and it's incredibly inexpensive.

Depending on your goal, you can use one or more conditioners. Try to read the label of any conditioner before buying or using it. This gives you an idea of ​​what they can do for you and whether they are sufficient for the tasks you have in mind.

For example, some products are classified as chloramine neutralizers even though they fight heavy metals. So if you can, you don't need to invest in a specific product to neutralize heavy metals.

(Video) API Tap Water Conditioner | Making tap water safe for your fish

Related articles that may also interest you:


Most water conditioners don't require you to remove the fish. You can pour the right amounts into the existing tank while the fish are in it. However, small tanks require special care. This means avoiding high levels of conditioner.

If you want to go without commercial products, you can boil water to condition. Boil water for at least 8 minutes to eliminate ammonia and chlorine contained in tap water. Either way, be sure to let the water sit for at least 24 hours before adding it to your fish.




1. Are Water Conditioners necessary for your aquarium? "TANK TALK" Presented by KGTropicals
2. How to Condition Water for Betta Fish?
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3. Prevent Fish/Aquarium Death! You Oughta Know About Water Conditioners!
4. THIS IS WHAT HAPPENS WHEN you do Not Add WATER CONDITIONER to your African Cichlid Fish Tank
5. Is Tap Water Safe For Your Aquarium? |
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6. Seachem Prime - How to Use on Water Changes
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