Why Does Tap Water Kill Goldfish?

by / Mar 20, 2019
What does tap water do to fish?

Can tap water kill you? Probably not. But have you ever thought about tap water's effect on a goldfish?

Most people have experienced bringing a goldfish home from the pet store (or maybe you won it at the ring toss booth at the county fair), and you had to add those extra water conditioner drops so that the goldfish can have a better chance to survive in tap water. If you didn't add the drops, there's a high likelihood that you'd find the fish belly up the following day, and you'd either send them to swim with the other fishes (down the toilet) or perform a proper burial in the backyard.

Many people have wondered if goldfish can live in untreated tap water. We know to be wary of contaminants in our tap water, but what about the water you give your pets? Should you be worried about the tap water you add to your goldfish's tank? The answer is yes! If contaminants found in plain tap water are harmful to humans, think of how horrible it is to let your tiny goldfish live in that water.


Best water for gold fish

Is Tap Water Safe For My Fish?

One of the most common questions that new fish owners ask is whether tap water is safe for their freshwater fish. The answer is no, not really. It can contain chemicals, minerals, and heavy metals that can be harmful to fish. The chlorine and chloramines commonly added to tap water to disinfect it can be toxic to fish and other aquatic animals. Tap water can also contain high levels of minerals such as calcium and magnesium, which can affect the pH and hardness of your aquarium water.

These factors can negatively impact the health and well-being of your fish, so it's important to ensure that you provide clean water in your aquarium to keep your fish safe and healthy. In the following sections, we'll explore some key factors to consider when it comes to providing the best water for your fish, including the benefits of filtered water and how to properly treat tap water to make it safe for your fish.

If you do use tap water for your fish, be sure to read the following guidelines to keep your fish safe and healthy:

  1. Allow tap water to sit: Before adding tap water to your fish tank, it's important to let it sit for at least 24 hours. This allows chlorine and other harmful chemicals to evaporate naturally.
  2. Use a water conditioner: Conditioned water is important for fish health because it helps to remove harmful chemicals and toxins from tap water, making it safe for fish to live in. Look for a conditioner that neutralizes chlorine and chloramines, detoxifies heavy metals, and promotes the growth of beneficial bacteria
  3. Adjust the pH: Tap water can have a high or low pH level, which can stress out your fish. Use a pH test kit to determine the pH level of your tap water and adjust it to the appropriate range for your fish.
  4. Check for water hardness: Tap water can also contain minerals such as calcium and magnesium, which can affect the hardness of your aquarium water. Use a water hardness test kit to determine the hardness level and adjust it if necessary.
  5. Maintain proper water temperature: Ensure that the water temperature in your tank is within the appropriate range for your fish, using a reliable aquarium heater and thermometer.
Monitor ammonia levels: Ammonia is a toxic compound produced naturally in fish tanks due to fish waste and uneaten food. When ammonia concentrations in the tank rise to high levels, it can be dangerous for your fish and lead to health problems like stress, fin rot, and even death.

Which Contaminants Are Dangerous For My Fish?

Chlorine and chloramine can be particularly detrimental to your fish's health. Luckily, Clearly Filtered water filters remove up to 99.5%! Nitrates and nitrites should also be removed, and our filters are able to take out up to 99.9%. A buildup of nitrates in your fish tank can lead to excessive algae growth, and high levels of nitrites can reduce the oxygen content in your fish's blood, so make sure to do regular water changes! You can also consider adding aquarium salt to reduce the level of nitrites. As always, when changing your water, make sure the new clean water is at a similar temperature to the water in the tank. Large fluctuations in temperature may shock your fish.

Does The PH Level Of My Goldfish Water Matter?

You may have heard someone recommend using distilled water instead of tap water for your fish tank. This is fine initially, but will eventually create a volatile environment that may allow the PH to fluctuate too much. These PH fluctuations can create an unhealthy environment for your fish and stress or even kill them in the long run. Clearly Filtered pitchers are able to leave behind the good minerals (or Total Dissolved Solids) in the water, which will act as a buffer for PH fluctuations in your water. This will make your fish's water the closest it will come to natural, contaminant-free water. When changing your fish's water, about 10-25% of your water should be removed and replaced with clean, filtered water. Remember to check the PH water parameters every time the water changes! A healthy range for most fish is between 6.5-8.2.

What Is The Ideal Water Temperature For My Goldfish

The ideal temperature for filtered water in a fish tank will depend on the specific species of fish you have in your tank. In general, most freshwater tropical fish like tetras or betta fish require a water temperature between 75-80°F (24-27°C), while coldwater fish like your goldfish prefer a slightly cooler temperature between 65-75°F (18-24°C).

It's important to research the specific temperature requirements of your fish species and adjust the temperature of your water accordingly. Maintaining a consistent water temperature is also essential, as sudden fluctuations in temperature can stress fish and make them more susceptible to disease.

Some filters and air pumps can generate heat that can raise the water temperature, so be sure to monitor the temperature regularly and adjust the filter if necessary.

Maintaining the correct water temperature is an important factor in ensuring the health and well-being of your fish, so be sure to research the temperature requirements of your specific fish species and monitor the water temperature regularly.

What Is The Best Water to Use For My Goldfish

Filtered water is a great option for your goldfish tank. Filtering your tank water removes impurities and contaminants such as chlorine, lead, and other harmful substances that can negatively impact the health and well-being of your goldfish. By using filtered water, you can ensure that your goldfish are swimming in water that is free of harmful chemicals and pollutants.

In addition to being healthier for your goldfish, filtered water can also improve the overall appearance of your aquarium. Filtered water is clearer and less cloudy than tap water, which can help showcase the vibrant colors of your goldfish.

Can I Use Bottled Water For My Goldfish?

You can use bottled water for your goldfish, but it's important to choose the right type of bottled water. Some are not suitable for goldfish and may contain minerals and other substances that can be harmful to them.

If you choose to use bottled water for your goldfish, look for a brand that is low in minerals and has a neutral pH level. Avoid using distilled water, reverse osmosis water, or water labeled as "purified" or "drinking water," as these may be too pure and lack essential minerals that goldfish need. Instead, look for spring water or mineral water that is labeled as suitable for drinking.

Keep in mind that using bottled water for your goldfish can be more expensive than using tap water or filtered water, so it may not be the most practical option for everyone. If you do decide to use bottled water, make sure to test the water regularly to make sure it maintains a stable pH level and that the water quality is suitable for your goldfish.

What Else Does My Goldfish Need to Stay Healthy?

Your tank is a small ecosystem, and it's important to keep it healthy. Here are a few quick tips to help you keep your goldfish happy and healthy.


Chlorine is a chemical disinfectant that is commonly used to treat tap water and make it safe for human consumption. However, chlorine can be harmful to goldfish and the beneficial bacteria in their tank.

When chlorine is added to tap water, it can kill off the good bacteria in your goldfish tank that help to break down ammonia and nitrite, which are toxic waste products produced by your goldfish. Without these bacteria, ammonia and nitrite levels can quickly rise and become toxic to your goldfish, causing stress, illness, and even death.

Chlorine can also cause irritation to your goldfish's skin and gills, making them more vulnerable to bacterial and fungal infections.

Using a water conditioner that removes chlorine and other harmful chemicals from tap water is essential for the health of your goldfish. Water conditioners neutralize chlorine and other chemicals, making tap water safe for your goldfish and preserving the beneficial bacteria in your tank.

If you don't use a water conditioner and still want to use tap water for your goldfish, it's recommended to let the tap water sit for at least 24 hours before adding it to your tank. This will allow the chlorine to dissipate naturally, although it may not remove all of the other harmful chemicals in the water.

Overall, it's best to use filtered water or water treated with a water conditioner to provide the best water quality for your goldfish and maintain a healthy environment in their tank.

Proper diet

Providing your fish with a well-balanced and appropriate diet is important for their overall health and well-being. Different fish species have different dietary requirements, so it's important to research the specific needs of your fish and feed them accordingly.

Appropriate tank size

Providing your fish with an appropriate tank size is important for their health and happiness. Different fish species have different space requirements, so be sure to research the specific needs of your fish and their tank mates to provide them with a tank that fits their size and behavior.

Regular tank maintenance

Performing regular tank maintenance, like water changes, filter cleaning, and substrate vacuuming, is important for maintaining good water quality and preventing the buildup of harmful substances and bacteria like e-coli in the tank.

Proper tank decor

Providing your fish with appropriate tank decor, like plants, rocks, and hiding places, can help reduce stress and provide a more natural environment for your fish.

Do you have customers that use Clearly Filtered water for their fish tanks?

As a matter of fact, we do! We often hear that a customer's fish loves swimming in Clearly Filtered water. We get a little giggle out of it every time we hear it, but it makes sense. Our filters are designed to target the contaminants that are known to cause issues for fish. The best part is that this shows us our filters are working as intended.

"Maybe the best review I could give comes from Bob, my pet Betta fish! Using treated tap water, the one-gallon bowl must be changed weekly, sometimes more often than that. I decided to use Clearly Filtered and am going on week four without needing to change his bowl, which remains as pristine as when first set up (without aquarium filter). If a water source is good or bad for living creatures, the same goes for people. Very happy with the peace of mind this filter provides, making it worth every penny spent to rid the tap water of Fluoride, lead, etc ..."

 - Mary Anne

Obviously, our filters are formulated for human use, but it is not uncommon that we hear about our filters being used for people's pets. Some even state that their animals will no longer drink regular tap water after trying Clearly Filtered (again, makes sense as their sense of smell and taste is far superior to that of a human). 

Best water for pets

We don't want to guarantee this will work for everyone or every pet, seeing as we have not specifically tested it ourselves; however, our customers love sharing their real-life scenarios with us, so we are fairly sure if it works for them, it will work for you.

So, what can I learn from this?

Other than animals loving Clearly Filtered water too, we learned that tap water contains levels of contaminants that can be deadly for smaller organisms like fish, and these same contaminants will have negative effects on larger organisms like plants and human as well.

The point is to let your filter do the work rather than turning your body into a filter. 

Oh, and always remember our number one fishkeeping rule: replace the water in your fish tank with fresh water once a week and let your filtered water come to room temperature before changing it. Your pet fish will thank you!

Let us know: Do you use Clearly Filtered water for your pets? If so, do they enjoy it?