Can Goldfish Survive in Tap Water?

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Tap water seems clean and clear. Perfect conditions for your pet goldfish, right? You might have already guessed it: Tab water often contains substances, that are not good for your goldfish. Some of these substances are so dangerous for your pet, that they could be killed in just a couple of hours!

As a whole, goldfish cannot survive in normal, untreated tap water. It contains substances that are no problem for humans but can be very harmful to your pet goldfish. It can burn the gills of goldfish, making it hard for them to breathe, and will eventually kill them.

So don´t put a goldfish in simple tap water. The water has to be prepared over several days before you can put the goldfish in it.

Is Tab Water Dangerous for Goldfish?

Goldfish can notice immediately if the water is suitable. If the water is really bad, a goldfish might even try to jump out or swim to the surface quickly and gasp for breath. But the chemicals in tap water can really harm a goldfish and burn the gills, which must be painful.

Imagine, you are being thrown into a pond of acid. You will probably also try to get out as quickly as possible.

But what is in tab water that’s so harmful and what does your goldfish need instead?

Tab water can differ from country to country, making it hard to say what’s exactly in your tab water. But you can learn how to treat your tap water so that it’s perfect for your goldfish.


Chlorine is in all tab water. It is important for us humans because it fights off bacteria, which could make us sick.

But goldfish are not like humans. They don’t like chlorine. It can irritate fish’s gill membranes and will attack their mucous coatings. These damages can make it hard for your goldfish to breathe. 

Therefore chlorine needs to be neutralized when you do a water change or you first fill up the fish tank. 


Some municipalities use chloramine instead or in addition to chlorine. It has a similar effect on goldfish like chlorine.

Both chlorine and chloramine have to be neutralized to make the water suitable for goldfish.

Heavy Metals

In addition to chlorine, you can often find heavy metals in water. The heavy metals are broken down into tiny bits and cannot be seen with a naked eye.

Humans can tolerate these heavy metals, but for goldfish, some of the heavy metals can be life-threatening or can at least cause a lot of stress to the goldfish.

Some of the heavy metals that can be found in tap water are for example:

  • Manganese

This heavy metal is essential in our human bodies in very small amounts. It can be found in surface and groundwater.

In higher concentrations, it can be toxic to both humans and fish.

  • Bronze and Zinc

Bronze and Zinc can be introduced to the tank through tap water or through decorative plants with bronze or zinc leads. Make sure that nothing in the fish tank contains metal.

If you need something to hold down aquarium plants, make sure that it is acrylead which is painted.

Don’t keep goldfish in a container that is galvanized or use water from galvanized water tanks. Zinc is poisonous to goldfish in the form of galvanizing.

  • Arsenic

Arsenic is a toxic heavy metal, that results from natural processes like volcanic activity, but also from human activities such as pesticide production and mining.

Arsenic in higher concentrations can cause serious damage to our human bodies. 

It can get into a fish tank either through tap water or through tank decoration in the form of treated wood. Wood treatment often contains toxins such as arsenic to stop insect attacks or rot. 

If you use wood, always make sure that it is not treated.

The impact of arsenic on a tiny goldfish’s body can be deadly.

  • Copper

Copper is a very common heavy metal that can be found in tap water. When a pipe or other plumbing fixtures corrode, copper can get into the water supply.

In small amounts, it’s no problem for humans, but goldfish don’t like heavy metals at all.

If your goldfish acts weird, lethargic, or gasps for breath at the surface with gills distended, those are signs of metal poisoning.

How Long can a Goldfish Survive in Untreated Tap Water?

If you see any of the following signs on your goldfish, you should remove your goldfish from the water and put it in a mild salt bath.

You can put two teaspoons of non-iodized salt per gallon into the salt bath and let the goldfish relax. Meanwhile, you can check the water in the tank with test kits.

These are possible signs of your goldfish if something is wrong with the water:

  • Gills distended
  • Gasps for breath at the surface
  • Breathes heavily
  • Lethargy
  • Appears pale
  • Acts weird
  • Develops red patches on the body or fins

How to Make Tab Water Suitable for Goldfish

Don’t worry, there are ways to treat your tab water, making it safe for goldfish.

The chlorine has to be neutralized and heavy metals have to disappear from the water. This has to be done for every water change and of course when you fill the tank with water for the first time.

Sodium thiosulfate

Sodium thiosulfate can be used to neutralize chlorinated water. But if you are not sure if the tap water in your region also contains chloramine, you might rather want to go with a water conditioner, which neutralizes both chlorine and chloramine. 

Water Conditioner

A water conditioner is essential to treat the water in a way your goldfish can thrive. It neutralizes the chlorine in the tap water and can get rid of the heavy metal.

You can get a water conditioner in every pet store. There is a variety of water conditioners.

If you want to make sure that the water is safe, you can choose a conditioner, that removes both chlorine and chloramine, because depending on the area you live in, the municipality can use either chlorine or chloramine or both. 

Some conditioner even gets rid of the heavy metals in the water. 

Pre-Conditioned Water

If you don’t want to use a conditioner or you simply don’t trust your tap water at all, you can use pre-conditioned water from your local pet store. The bottled pre-conditioned water can be very handy for water changes but can be pricey if you don’t use a conditioner at all. 

To make sure that your goldfish are happy, check the parameters of your water with test kits from the pet store if you are unsure about the water quality, and also watch your goldfish. If they act weird, there might be something off with the water.

Never clean the filters or anything else from the tank, such as decoration, with tap water. These are the area, where the good bacteria lives, which will help you to maintain good water quality. If you wash these things, you will get rid of the good bacteria.

What are the Perfect Water Conditions for Goldfish?

With the perfect conditions, you will have a happy goldfish, that can live for years and years. These are the parameters, you should keep an eye on:


Between 66 and 74° F


The pH level shows how acidic or alkaline the water is. 7.0 is neutral. A good level for goldfish is between 7.4 and 7.9


Ammonia is highly toxic for your goldfish and has the potential to kill your pet in a very short time. It is a waste product, that the goldfish produces through poop. The level should be as low as possible. The best level would be 0, but up to 0.25 ppm would be tolerable.


When the ammonia is broken down by the “good bacteria” in the tank, it becomes nitrite. Nitrite is already less harmful than ammonia, but can still cause some serious health issues for your goldfish. Just like ammonia, the level should be as close to 0 as possible. 

If the level of nitrite is too high, it can make your goldfish suffocate.


Nitrate is a substance, that results from nitrite being broken down by good bacteria. Nitrate is a lot less toxic than ammonia or nitrite. The level should be somewhere below 40 ppm. If you experience greenish water or sudden growth of algae, the nitrate level might be too high.

How to Keep Your Water Clean

You don’t want to overcrowd your tank with fish. Every fish produces waste and goldfish are very efficient in waste production.

They poop a loooot! This is why they need enough space in the tank. Otherwise, the water quality will suffer.

The minimum space for one single goldfish is a tank with 20-30 gallons of water. For every additional goldfish, you should add 10 gallons of water. 

In addition to space, it is also important to keep the water clean. Water changes should be done regularly, at least once a week.

And of course, not only the water but also the gravel has to be kept clean. You can vacuum the gravel in the tank, you don’t have to remove it.

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