How To Add Water To Koi Pond Without Killing Your Fishes

How To Add Water To Koi Pond Without Killing Your Fishes

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Deciding to change and add water to Koi Pond frequently is an important routine to keep your fish pond in great shape and the koi fish healthy. This is because stagnant water becomes polluted with nitrogenous wastes that come out of the fish, decaying matter from bottom debris, and other organisms that grow in the pond. This can cause pollution problems resulting in reduced oxygen levels for your koi fish which can cause health issues or death if not attended to.

Before adding any freshwater to replace the old one in the koi pond, it is important to prep the new water you want to add and dechlorinate it if necessary. This is because the water in your koi fish pond contains dissolved wastes that add to the total load and these need to be deactivated before adding fresh water into the pond. It also helps kill any algae and bacteria that may have grown in the pond over time, keeping it clean and healthy for your koi fish.


Can You Fill A Koi Pond With Tap Water?

Yes, when contemplating to add water to koi pond, you can fill your koi fish pond with tap water but you will have to dechlorinate it. Topping up your koi fish pond with tap water is without dechlorinating is not recommended for the safety of your fish, and the reason is that tap water contains chemicals like chlorine that are designed to kill bacteria or other nasties, fluoride, and other minerals are also added to treat tap water, which decreases the sharpness of the taste, add oxygenation, etc. These are all things that are beneficial when it comes to drinking water but not so great for your fish in a koi pond.


How Long Before Tap Water Is Safe For Koi Pond Fish?

Depending on the quantity and ratio of the water to the pond, after changing your koi pond water it’s best to let the tap water sit for about 48 hours which is 2 days to allow enough time for the Chlorine to evaporate before you can add water to koi pond. Although it can be a little tricky deciding when tap water is safe to pour in a koi fish pond, even after dechlorinating it, there’s still uncertainty that it’s been completely free of chlorine or when it is.

While it’s safe to add tap water to a koi pond when the chlorine has been eliminated from the water, it is still recommended to add additional products such as Methylene Blue or AmQuel Plus to add other helpful bacteria and other healthy additions.


There are ways of telling whether tap water has been dechlorinated and one such way of checking is by adding a little bit of tap water to some test tubes and adding a few drops of household bleach, if it begins to fizzle or bubble the Chlorine hasn’t been completely removed from the water.

How To Add Tap Water To Koi Pond

After dechlorinating and sitting your tap water for about 48hrs to completely eliminate the chlorine, you are now ready to fill your koi fish pond with the dechlorinated water.

What you need:

  • A garden hose with a pressure regulator to control the water flow rate into your pond. You might wonder if you can use a hose to add water to the koi pond, yes you can.
  • A pair of gloves for protecting your hands from the koi fish in case they jump out of the pond while adding water.
  • A net for catching escaped fish and moving them back into the pond (optional).

Steps to add tap water to a koi pond

  1. Using a garden hose with a pressure regulator – attach one end of the hose to an outdoor spigot and place the other end into your pond so it is about 6 inches below the water’s surface.
  2. Turn on the spigot to fill the tank with tap water.
  3. When adding water to koi pond, be sure to leave space in your koi fish pond for additional filtration needs, maintenance and adding any future fish that might occur!
  4. After adding all of the water and adding any chemicals and dechlorinator, turn off the tap and allow the new pond water to sit in your koi fish pond for at least 24-48 hours.
  5. The chlorine should have dissipated by then. If not, you can add additional time or change out some of the pond water to get rid of the remaining chlorine.
  6. Turn the spigot back on to fill your koi fish pond.
  7. After adding tap water, be sure to check for any leaks if you have a small leak it will not be so visible and over time this could lead to severe problems adding tap water can also help reduce some of these issues.
  8. Make sure there are no leaks adding tap water can also help reduce some of these issues.
  9. Turn off the pump and remove the water level to your desired depth adding tap water can also help reduce some of these issues.

Your Koi pond should now be filled with water ready for your Koi Fishes.

How Long Can Fish Survive In Tap Water?

If you do not dechlorinate your tap water before pumping it into your koi pond with the fish in it, your fish might die within about 30 minutes to one hour. Chlorine is known to destroy the slime coat of a fish in about 30 seconds which is why dechlorinating your water before adding to your koi fish pond is one of the most important steps in replacing or topping up the water in your koi fish pond!


How Do You Make Pond Water Safe For Koi Fish?

A lot of fish ponds owners that have spent quite a while doing it are aware of the importance of good water for the fish. Without knowing the why and how it can be challenging for people to maintain a pond and ensure the pond water is safe for fishes living in it.

How do you make pond water safe for koi fish

So here are some of the most important things you must consider;

  1. Firstly; it is essential to ensure that your water sources safe for fish, whether you draw it from your home’s tap or use well water.
  2. Secondly; Fish ponds owners must test their pond water continuously and make sure there are no ammonia, nitrite or nitrate levels.
  3. While you add water to koi pond, aeration is important because it is a safe way of making sure the pond water is oxygenated. It also breaks down the pollutants in the pond and makes it safe for fish to swim about. However, when you aerate your koi fish pond, ensure that you check for nitrates as well as phosphates which can be harmful to fish if too much accumulates.
  4. Ensure that you keep your fish safe by getting rid of any sick or decaying leaves and plants.
  5. Ensure that there is a safe place for the koi to rest and safe hibernation spots like under the rocks and bog-wood.
  6. Taking a healthy fish population into consideration because excessive fish will lead to excessive waste which will ultimately cause an imbalance in your pond water.
  7. Create a proper balance of pond plant life to safe pond water by providing oxygen for the fish and safe havens for them.
  8. Ensure that your pond is safe from predators such as cats, dogs, raccoons and other mammals.
  9. Introduce beneficial bacteria to your pond water because they have a role of breaking down the nitrogen cycle. They also work to break down harmful ammonia into safe nitrate.
  10. Test the pond water every week; there are safe chemical kits that can help you test your pond water which is recommended if you have fish that are sensitive like Koi.
  11. Take out debris in the pond before it decays.


There are so many factors to consider when adding water and maintaining your koi fish pond which can be hard to keep track of. However, with these tips and techniques, you should be able to make it more manageable! Remember, safe water is the important thing you need to consider when keeping koi fish. So keep your pond safe by taking note of these points!