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Can Freshwater Aquarium Fish Survive in Tap Water? Answer

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Owning an aquarium means frequent water changes to keep your fish healthy, and to keep the water parameters in check. With that being said, adding regular tap water to the tank may be tempting for efficiency. 

Freshwater fish can not survive in tap water right out of the sink. Tap water is treated with chlorine, which is toxic to all fish and can kill them in a few days. Before any water is added to your freshwater aquarium, the chlorine must be removed. There are ways to remove chlorine from the water.

Untreated tap water will kill your fish due to the chlorine added to the water, but there are five different ways to remove the chlorine from the water to make it safe for any fish. 

Allow the Tap Water to Sit

Allowing the tap water to sit will cause the chlorine to evaporate from tap water after at least 24 hours, thus requiring at least that long to dechlorinate. It may take several days to dechlorinate all of the chlorine depending on how much was added by your water municipalities.

If you have a larger tank, therefore requiring more water for the water change, you can set up buckets of water in an isolated room a few days before the water change to provide an ample amount of time for the water to dechlorinate. 

Furthermore, allowing the tap water to be set at room temperature for a few days will cause less stress to the fish when the water is added to the tank. This is because the water will be at that room temperature and won’t cause a shock to the fish. 

Freshwater fish - Mikrogeophagus ramirezi

Boil the Water

Boiling water to remove chlorine from tap water is a possible option as well. If you let the water come to a boil for about 15 minutes, the chlorine will evaporate from the water along with other bacteria. 

Boiling the water is also beneficial when it comes to removing contaminants in the water that can cause several diseases in fish. However, this can be a long process, especially if you are trying to complete a more extensive water change. 

You would not only have to wait for the water to boil, but also allow ample enough time for the water to cool off as well. 

Use a Dechlorinator 

This is the most common option when doing a partial water change, or completely setting up a new tank. This is because using a dechlorinator, or water conditioner is the most convenient and quick to use. 

You can purchase a bottle of water conditioner at almost any pet store, which can be used when adding tap water to the tank. No waiting! Simply put room-temperature water in the buckets and add the correct amount of product to the water. 

When I do water changes, I typically put the tap water in the tank and then add the dechlorination closer to my bubbler to ensure that the product is spread around quickly. Make sure you read the instructions on the bottle as every product is different and you don’t want to add more product than you need. 

Use a Reverse Osmosis Unit

A reverse osmosis unit can come with a hefty price tag, but it is worth it if you have a larger fish tank. The reverse osmosis unit hooks up directly to your faucet and filters out all harmful chemicals including chlorine, nitrates, and phosphates.

It is also used as a water softener and can reduce acidity (pH) in the water. If you do have one of these units, you simply can add it directly to the fish tank as long as it is at the correct temperature. 

Use an Ultraviolet Light 

Purchasing an ultraviolet light bulb is a great option if you have a larger tank. You can put the tap water directly in the tank, and the light bulb will take care of the rest. So, how does this work?

The ultraviolet light bulb causes a reaction in the water which in turn neutralizes the chlorine in the water. The UV light also removes toxins such as ammonia and nitrate which is deadly to your fish as well.

On top of removing the above toxins, using an ultraviolet light in your tank will reduce the amount of algae growing in your tank. This can mean fewer water changes and an overall healthier tank. 

The downside to using an ultraviolet light without any other tank conditioners is the fact that these units do not remove any heavy metals. Heavy metals are unhealthy for your fish, so you should ensure your tank parameters by using test strips in your tank. 

How long will a fish live in tap water?

As mentioned, leaving fish in tap water will cause them to die, but not right away. If you accidentally added tap water without treatment, you can add the solution after. If you didn’t realize the mistake, a fish will likely only live up to a few days. 

Small amounts of chlorine will make your fish, but it is possible to recover. However, if there is a large amount of chlorinated water, they will die more quickly. Once the chlorine hits the fish, they will begin having skin lesions, difficulty breathing, and organ damage. 

With this being said, the sooner you realize the mistake, the better. How fast a fish dies from being put in tap water also depends on a few other factors. These include the size of the fish, species, and their metabolism. 

Best Water for Your Aquarium

Surprisingly, there is a multitude of different types of water out there that someone could put in their aquarium. With that being said, some are better than others. Below is a list of different water types and what steps are necessary to take for the water to be safe for your tank. 

  1. Tap Water: As stated, tap water is perfectly safe for fish just as long as the chlorine is removed from it. Tap water is also easily accessible as it is already in most homes.
  1. Well water: If you have well water at your home, then you are in luck. Well water is not typically treated with chlorine. However, each well is different. That said, you will want to test your water parameters to ensure other chemicals are not present before putting the water in your tank.
  1. Distilled water: Distilled water is essentially evaporated water that was collected after the base water was heated and cooled. During this process, many minerals are removed. You may need to remineralize the water depending on your water parameters after you test them. Distilled water does not have chlorine. 
  1. Spring water: Spring water does not contain any chlorine and is very healthy. Spring water typically carries a multitude of minerals and can be added directly to your aquarium. Again, you should always test the water to make sure your tank parameters stay in check.
  1. Rainwater. Some people prefer to collect rainwater for use in the household. However, it is not recommended for fish tanks. This is because rainwater can have an unpredictable pH. There are also several minerals missing from rainwater, and the water can also become contaminated by hitting roofs on the way down.