How Long Does It Take for Tap Water to Be Safe for Pond Fish?

The amount of time it takes for tap water to be safe for pond fish depends on your use’s dichlorination method. If you choose to let the water stand, you’ll need to give it 24 hours to 48 hours. The time will depend on your pond’s size and how chlorinated it is.

Other methods such as water conditioners and carbon filters work much faster. For example, a water conditioner can take about 15 minutes to dechlorinate tap water and make it safe for fish. That is why it’s safe to add the conditioner directly to the pond with the fish inside.

Carbon filters, especially hose attachments, can work almost instantly. But, again, these are estimated times. The exact time may increase if you’re dechlorinating a large pond.

Our Favorite Pond Dechorinators

Is Tap Water Safe for Pond Fish

Tap water is safe for pond fish if it does not contain chlorine, chloramine, or other chemicals. Most water suppliers add some chlorine to the water to keep it clean and safe for human consumption. However, it does not have the same effect on pond fish.

So, you will need to remove the chemicals from the tap water before you add your fish into it. If you change your pond water often, make sure not to change all of the water at once. Drastic changes to the water’s parameters (i.e., the temperature, pH value, mineral content, and so on) can shock your fish and make them sick.

Will Tap Water Kill My Pond Fish?

High amounts of chlorine can be highly toxic to pond fish. So, it can also kill your fish if you don’t treat it. So, when you decide to create a pond in your home or other space, you must also determine the water source beforehand.

You should make sure that the water source is safe for pond fish. When using tap water, make sure to have dichlorination systems ready, and plan how often you’ll partially replace the water. You should not return more than 10% of the pond water at a time.

You should partially replace the water in your pond about once a week. If you don’t, the concentration of pollutants increases because the water evaporates.

There won’t be an adequate balance of the necessary parameters when you don’t replace the water. The toxins can start with making your fish sick, and it can eventually kill them. Therefore, when partially replacing the water, make sure the tap water does not have pollutants present.

How to Dechlorinate Tap Water for Your Pond and Make It Safe

There is more than one way that you can remove chlorine from your tap water. What you pick will depend on the size of the pond, how untreated the water is, and, of course, your budget. With that said, here are a few ways on how to dechlorinate tap water for pond fish.

Let the Tap Water Stand

This method is used when you want to remove chlorine only. This method is also known as aeration or aerating your tap water.

So, before you put the tap water into a pond, put it into a large bucket. Next, let it stand for about 48 hours.

The chlorine content in the tap water will rise to the water’s surface and evaporate after that point. This method is ideal if you’re operating on a low budget (which is likely for most people) and for small ponds. You won’t have to spend money on any additional equipment.

This method may also work in 24 hours, but that will depend on the amount of chlorine present in the water. Furthermore, you should note that this method will not work with chloramine. This is because chloramine is a heavier substance than chlorine and won’t rise to the water’s surface.

That is why it’s best to get in touch with your water company to learn if there are traces of chloramine in the water. On the other hand, you could test the tap water yourself for ammonia (chloramine).

Consider a Pond Aerator

If you plan to use aeration as your primary dechlorination method, consider investing in a pond aerator. A pond aerator is a mechanism that speeds up the aeration process.

So, you can add your fish to the water quickly. This can be helpful if you have already purchased your fish but don’t have a place to keep them.

Water Conditioner (A De-chlorinator)

A de-chlorinator, i.e., a water conditioner, is probably your safest option for dechlorinating tap water for pond fish. This method is also one of the most common ones because it removes chlorine, chloramine, and other substances.

So, it’s a great choice if you plan to use 100% tap water for your pond. That said, it’s always important to double-check the label if the water conditioner removes chloramine as well.

The Types of Ponds Water Conditioners Are Best For

You can use this method for both small and large ponds. However, you will have to vary the amount of conditioner you use based on the pond’s size. Make sure to read the product’s label for proper dosing.

Excessive amounts of water conditioner can be harmful to your fish.

How to Use Water Conditioners

There are two ways to use a water conditioner. The first is to fill a bucket of tap water and add the conditioner to it. The second method is to add it directly to your pond water, even if the fish are inside the pond.

So, this method can make the process of changing the water easier. This is because you can add the water and conditioner at the same time. That said, make sure to check the label to determine if it’s safe to add the conditioner directly to the water and while the fish are present in the water.

Activated Carbon (Charcoal) Filters

An activated carbon charcoal filter is necessary when you need to remove particularly heavy organic pollutants from your tap water. So, you can use these filters to remove substances that bio and machinal filtration can’t. Here’s what you should know about how to dechlorinate tap water for pond fish with an activated carbon filter.

The Pollutants Activated Carbon Filters Remove

An activated carbon filter uses a process called adsorption. What happens is that the pollutants get stuck to the carbon. After that, the carbon neutralizes the harmful substances back into the water, making them safe for your gilled friends.

Some of the pollutants that such filters remove include:

  • Chlorine
  • Chloramine
  • Pesticides
  • Tannin
  • Medicines
  • Perfumes

Consider this dichlorination method if your tap water is typically hard and not safe for human consumption.

Activated Carbon Filters Can Be a More Expensive Option

Now, because it removes so many substances, an activated carbon filter can be a little heavy on your wallet. Perhaps what makes it even more expensive is that you’ll have to replace the carbon surface every 2 to 3 months. In that much time, the carbon surface will be covered with pollutants and won’t work correctly.

Though the carbon itself is relatively affordable, it’s the consistent changes that can prove to be expensive over time. You can expect it to be even more costly if you have a relatively large pond.

That said, one of the most significant advantages of an activated carbon filter is that it makes the water clear. So, you can show off your fishies to your guests with ease.

How to Use an Activated Carbon Filter

You can use an activated carbon filter in the same way as a water conditioner. For example, you can choose to treat the tap water in a bucket before adding it to the pond, or you can install the filter in the pond and let it cycle the water.

The second option will reduce the chlorine content and increase good bacteria for your fish. So, it’s an excellent tool for a new pond. However, if you choose the first option, ensure that the fresh water has similar parameters as the existing pond water.

Garden Hose Filter Attachment

Now, if you’re like most people, you probably use your garden hose to fill your pond. If you don’t, consider it because it’s a quick and efficient system. That said, you’ll need a carbon filter garden hose attachment if you choose this way to fill your pond.

Use a Carbon Filter Hose Attachment Best for Your Pond

You should get a product that has a high capacity to treat the water (more than 5000 gallons). This way, you won’t have to spend effort and money constantly replacing the filter attachment. You can then safely use this attachment for a large pond as well.

Make sure to use a product that has good reviews. The water will instantly pass through the filter. So, it should remove all chlorine and chloramine as soon as the water makes contact with it.

What to Keep in Mind When Using a Carbon Filter Hose Attachment

Now that you know how to dechlorinate tap water for pond fish with a carbon filter hose attachment, you can start to see how it’s a convenient option. That said, it’s recommended that you don’t fill the water directly into the pond through the hose.

The reason for that is that the temperature of the water may not be consistent. The temperature of the tap water must match the pond water to prevent shocking your fish. So, fill the tap water in a bucket before you transfer it to your pond.

Boiling Your Water

Boiling your water is one of the most cost-effective methods to dechlorinate tap water for pond fish. Boiling water causes the chlorine atoms to gain more energy because they get hotter. As a result, they rise to the top and eventually evaporate.

The boiling process will take about 15 minutes to remove the chlorine content altogether. Make sure to start counting the time after the water starts bubbling.

Drawbacks of Boiling Water for Dechlorinating Tap Water

Boiling tap water is similar to aerating it (letting it stand for a day or two). So, it only removes chlorine—not chloramine and other chemicals.

Even if your water source has only chlorine, another concern is the pot’s size. Unless you are a witch with a giant pot, you won’t be able to boil large quantities of water at a given time. So, this method is feasible for small ponds.

If you choose to use this method for large ponds, you will spend a lot of time, effort, and money. You’ll have to keep your stove or electric heater running for hours to boil enough water to fill the pond. This is especially so if you’re filling a new pond.

Will Aerating My Pond Help Dechlorinate Tap Water?

Yes, aerating your pond will dechlorinate tap water, but it will only remove chlorine from tap water. Also, it’s a more effective method for relatively small ponds. If you choose this method, don’t let your fish in the tap water until it’s wholly aerated and dechlorinated.

How Long Should You Wait Before Adding Fish to Your Pond?

There’s no precise answer to how long you should wait before adding fish to your pond. However, you should only add your fish to your pond when all of the parameters are correct for your specific fish. So, the waiting period will vary based on how long it takes for the parameters to be met.

It would be best to research the specific fish you plan to keep in your pond. Some fish have more demanding parameters than others. So, looking that up will help you better understand how long you should wait before adding fish to your pond.

That said, if you don’t have a heater in the pond, you should wait for at least 72 hours before you put your fish into your pond. But, of course, this is also the case if only the water is new in the pond.

Seventy-two hours will be enough for the temperature to set and stay stable. When the parameters are set, make sure not to dump your fish in the pond directly. Doing so will shock your fish and cause them to get stressed, which can be catastrophic to their health.

Pro TipYou should slowly add a bit of the pond water into the container that your fish is in. This way, your fish will begin to get used to the water in the pond.

Continue replacing the water bit by bit after every 15 minutes or so. You can then release your fish into the pond.

What Is the Best Water to Use to Fill a Pond?

There are several water sources that you can consider for filling your pond. Whatever source you choose, make sure that it does not contain chlorine and other harmful chemicals. However, it should contain essential minerals for the fish to thrive.

Tap Water

Tap water is an excellent source for your pond as long as you dechlorinate it properly. Since it’s made for your consumption, it has a relatively stable pH value and includes minerals and other nutrients.

Make sure that you choose a dichlorination method that also removes chemicals such as chloramine and fluoride. Next, you can get a water testing kit to determine which chemicals are present in your tap water. After that, you’ll know which dechlorination method will work best in your case.

You could also have your water supplier send you a detailed report on the chemicals present in the tap water. In most places, water suppliers are obligated to do so if you make a request. This way, you’ll have a more accurate overview of what’s in your tap water.


Rainwater may be nature’s water supply, but it’s not an ideal water source for pond fish. This is because it’s just water and doesn’t contain minerals and other essential nutrients. Fish and other animals need these minerals and nutrients to grow and stay healthy.

At the same time, rainwater has a high chance of picking up contaminants from the atmosphere. These contaminants include acids and sulfides. Such contaminants can lower the pH value of the water, making it more acidic.

In addition, rainwater is low in alkalinity and hardness, which is needed to thrive. So, rainwater tends to have an unstable pH value. This means that it’ll be more challenging for you to keep stable parameters in the pond water and prevent shocking your fish.

If you have a steady supply of rainwater in your area, you can consider mixing some of it with dechlorinated tap water. This way, you can ensure the necessary nutrients are present in the water. That said, it’s best to avoid using rainwater for your pond fish.

Boiled Water

Boiled water can be a safe source of water for your pond fish. It is also one way on how to dechlorinate tap water for pond fish. However, you can only use boiled water if it contains chlorine only. You should not use boiled water if its source contains chloramine.

Distilled Water

Distilled water is not ideal for pond fish. Even though it doesn’t contain harmful chemicals, it doesn’t have essential minerals in the water that fish need to stay nourished and healthy.

You could consider mixing a bit of spring water or tap water with distilled water to include the necessary minerals. However, it would be best if you didn’t take that risk because you may end up harming your fish.

Video: How To Top Up Pond Water


Take a look at some frequently asked questions about pond fish.

Why Do My Fish Come To The Surface When I Add Tap Water To My Pond?

Your fish will come to the water’s surface if there is a lack of oxygen in the water. This is because there is more dissolved oxygen content in the water you added.

A lack of dissolved oxygen occurs when there’s poor water quality or a lack of aeration. The lack of oxygen can stress your fish, putting their health at risk. It also makes them more susceptible to diseases and parasites.

At that point, you should perform a quick check of possible causes for the issue. For example, check if there’s a dead fish in the pond, and remove it immediately if you find one. In addition to that, take a quick look if your aerators are working correctly.

If you can’t find any possible causes for the problem, you may not be partially replacing your water frequently enough. This means that the water quality is not staying consistent and clean enough for your fish to survive, let alone thrive. Partially replacing the tap water frequently ensures that the ammonia and nitrate levels are acceptable in the pond water.

How Much Tap Water Can You Add To Your Pond Without Hurting Your Fish?

The amount of tap water you should partially add will depend on a few factors. These include the:

  • size of your pond
  • number of fish in your pond
  • number of plants in your pond
  • type of plants you have, like lilies or bog plants.
  • quality of water that you typically use
  • filtration system you use and its effectiveness

That said, it’s best to remove and add only small amounts of dechlorinated tap water to your pond at a time. You can estimate removing and adding only about 10% or less of the total water in your pond. Anything more than that can change the parameters in the pond water and make it unsafe for your fish.

Last Few Words

Your fish’s health and lives depend on your knowledge of how to dechlorinate tap water for pond fish. This way, you can determine which method is best suited to the tap water from your supplier.

It’s always best to purchase a water testing kit. It will remove any doubts about the water quality you’re putting into your pond. After that, your fishies can enjoy their home with clean and safe water.


Jack Dempsey