Can You Use Bottled Water to Fill Your Fish Tank

Bottled water is usually drinking water that has been cleaned in some way. It can be distilled water, reverse osmosis water, or cleaned spring water. While bottled water is generally clean and safe for drinking, most bottled water brands are not a good option for filling your aquarium.

You may also like:

Below are some of the reasons why most bottled water brands are not a good option for filling your aquarium.

  1. Most bottled water brands have no minerals for pH buffering. This is because the water in them is usually either reverse osmosis water or distilled water (both are products of processes that eliminate minerals). The lack of minerals and the subsequent lack of pH buffering in your fish tank can result in an unstable pH, which will be dangerous for your fish.
  2. Most bottled water brands are chlorinated to kill germs and bacteria. While chlorinated water is safe for drinking, it is dangerous for your fish and other aquarium life. 
  3. Distilled bottled water brands can kill your fish. This is because pure distilled water can cause the salts in your fish’s blood to diffuse out through osmosis resulting in neurological and other serious problems. 
  4. Spring bottled water brands can lower the pH and the hardness of your fish tank water. This may make your fish tank water unsuitable for your fish if your fish only tolerates higher water pH and hardness.
  5. Most bottled water brands are expensive to use to fill your aquarium.

There are obviously some bottled water brands especially mineral water brands that you can use to fill your aquarium. However, most brands are not good options for the reasons stated above. 

Types of Bottled Water


Bottled spring water is not very suitable for fish tanks. This is because most spring water brands have low or acidic pH values. This means that if you buy one it will most likely be slightly acidic or low. This is not very suitable for fish tanks because most aquarium fish are adapted to living in slightly alkaline water. 

Therefore, if you fill your fish tank with somewhat acidic bottled spring water, your fish won’t stay very healthy. They can adapt to the low pH value water but they will not be very healthy. If you continue filling your fish tank with bottled spring water, your fish could get sick and die. Things are that serious.

However, if you keep a South American aquarium fish species, then it is very likely that it does not mind low pH value water. Therefore, chances are that most of the bottled spring water brands in your local store are safe for your fish. However, you should not just assume this. Do research before you fill or start adding spring water to your fish tank.

Sparkling water

Sparkling water is a no for fish tanks. It is not suitable because by definition it is water that contains dissolved carbon dioxide gas. 

Dissolved carbon dioxide gas may be for the plants in your aquarium but it is not so good for your fish. This is because it will automatically lower the pH value of your fish tank water and make it acidic and toxic for your fish.

So bottled sparkling water does make your fish tank water very conducive for fish or any other life for that matter. Avoid it like plague. 

Distilled water

Because bottled distilled water is clean and purified water, using it in your fish tank may seem like a safe and wise thing to do. However, it is not. While your fish won’t mind staying or swimming in clean and purified water, they will mind the lack of minerals in it.

Because distilled water is made in such a way that it has little or no dissolved solids, it has no minerals. And the fact that it has no minerals means it is not suitable for aquatic life. This is because minerals are important for the wellbeing of fish and underwater plants. Minerals also help to stabilize the pH value. 

The lack of dissolved solids in distilled water means it is the softest type of water in the world. You can, therefore, use it to soften tap water before you do a water change. 

Furthermore, if you re-mineralize distilled water, you can use it to fill your aquarium since it will be very clean and healthy water for your fish and plants.

Reverse osmosis water

Reverse osmosis (RO) bottled water is very clean water just like distilled water. It is water that is purified in such a manner that it ends up with no impurities, no ions, and neutral pH.  While it is very clean water, it is also water that has not very conducive for fish.

It is not conducive for fish because it since its ions are removed, it can significantly change its hardness, alkalinity, or pH when exposed even to small quantities of any chemical. Therefore, it is not easy to maintain its stability.

Moreover, the fact that it has no minerals means it is also not very conducive for aquatic life just like bottled distilled water. So you cannot use it to fill your fish tank. 

Only experienced fishkeepers who are experienced and can properly manipulate aquarium water can use bottled reverse osmosis water to achieve the perfect water conditions for their aquariums.

Deionized water

Deionized water is simply water without any ions. It is not very safe for fish because it lacks minerals. In fact, it is not even very safe for drinking. Several studies by reputable organizations show that it results in the loss of electrolytes in humans. Therefore, it follows that it will not be safe to keep your fish in it because it will negatively affect their electrolytes and their ions.

Mineral water

The most popular bottled water brands are mineral water brands. In fact, when somebody mentions bottled water, your mind will most likely think they are talking about mineral water. 

Mineral water is the best type of bottled water for fish. This is because it has got minerals and ions such as calcium and magnesium that fish and plants need for wellbeing. The minerals and ions in mineral water also act as a buffer for pH. So generally speaking, you can safely use most mineral water brands as aquarium water.

However, not all mineral water brands are safe for fish tanks. This is because some of them contain minerals such as chloramine, chloride, arsenic, aluminum, and fluoride that are not suitable for fish. Therefore, you should avoid using mineral water brands that have any of these chemicals, especially at high levels. Nevertheless, it is important to mention that most mineral water brands will probably not contain such minerals in the first place. However, there is no harm in being cautious and checking the mineral content label of the brand you want to use.

Many aquarists successfully use mineral water to sustain their fish and other aquarium life. The aquarium fish that are known to do well in mineral water include angelfish, oscars, killifish, swordtails, goldfish, zebra danios, mollies, neon tetras, guppies, and betta fish. Simply put, the most popular aquarium fish can thrive in mineral water aquariums.

In summary, the best type of bottled water for fish tanks is bottled mineral water. 

Bottled Mineral Water versus Tap Water

Tap water is the recommended water for aquariums. This is because it is cheap, it is readily available, and it has the minerals and ions that make it conducive for aquatic life. 

However, while tap water or municipal water is recommended for aquariums, it is often not used directly. This is because most municipalities across the world add chlorine to it to kill the micro-organisms. And while chlorine is very effective at killing micro-organisms, it is virtually harmless to human beings. So you can drink water with traces of chlorine in it as you have been doing all your life if you use municipal water.

Nevertheless, while the chlorine in municipal water is not harmful to you, it is harmful to fish. If you fill your fish tank directly with tap water, the chlorine in the water could make your fish sick or kill it or them. To remove chlorine from tap water, aquarists usually add a water conditioner or let the water sit for a while. 

From this information, I am sure you can tell that tap water is cheaper and more convenient to use to fill your aquarium and/ or do water changes. However, you must remove the chlorine from it before using it. If you can afford to use mineral water and you do not mind the work it involves to get it into your fish tank, then go ahead and use it. Just make sure it does not have minerals that are not conducive to your fish.

Additives that you can add to different types of bottled water to make them suitable for your fish tank

Water conditioner 

Most bottled water brands have chlorine or chloramine in them and this can be dangerous for your fish. Chlorine or chloramine is usually added to bottled water to kill germs and bacteria. However, neither of the two chemicals is safe for your fish. So to safely add a bottled water brand that has either of the two chemicals in it to your fish tank, you need to eliminate the chemical.

The chemical products used to eliminate chlorine or chloramine from water are known as water conditioners or dechlorinators.  So you need to buy a water conditioner and add it to your chlorinated bottled water before using it to fill your aquarium. There are many water conditioner brands available both online and in pet stores. Just find one that is effective and use it.

Aquarium salt

Many reverse osmosis and distilled water bottled water brands available on the market do not have salts or minerals. This is because both reverse osmosis and distillation water purification processes clear minerals from water. And water without minerals is not safe for fish. There are several aquarium salt products on the market that you can buy to re-mineralize distilled or RO bottled water to be able to safely use it to fill your fish tank.

As you can see, it is just too much work to use bottled water for your aquarium. Below are other sources of water you can use for your aquarium. The first one is the cheapest and the most convenient to use.

Other sources of water for your aquarium and what you need to know about them

Tap water 

This is the cheapest and most convenient source of water for aquariums. However, it must be treated using a water conditioner since tap water is always treated with either chlorine or chloramine. Apart from using a water conditioner, tap water can be left to sit to eliminate the chlorine or boiled to eliminate chlorine.

The best thing about tap water is that it is cheap and you can just get it straight from your tap. Unlike some bottled sources of water, tap water has got minerals. This means it is healthy for fish. However, before you start using your tap water for your aquarium, you should fetch a sample and send it to your local pet store or lab to get it tested. This will help you know if the water has a pH that your fish can tolerate.

Reverse osmosis water

If you have a reverse osmosis water purification unit, you can make very clean water for your fish. This is because reverse osmosis water purification makes very clean water. However, it also removes minerals. So before adding reverse osmosis water to your fish, you should add aquarium salt to remineralize it and make it healthy for your fish. 

Distilled water 

Like osmosis water, distilled water is water that has been purified. It is very clean and one could assume that it is also safe for fish. However, distilled water typically does not have minerals in it. Nevertheless, it can be remineralized using aquarium salt.

However, you should note that using reverse osmosis water or distilled water will be expensive for you in the long run since you actually have to regularly change the water in your fish tank even if you have a filter. Nevertheless, if you can afford to use distilled water or osmosis water for your fish tank, you should go ahead and do it but make sure you remineralize it first. 

Local water body water

Is there a river flowing close to where you live? Or there any other natural water body close by? If there is and you have seen fish in it then you may assume that it is probably the best water for your fish tank.

However, this is not always true. The water could be polluted or could have minerals that are not very friendly for your fish. So before you draw water from a local water body to add to your fish tank, take a small sample of the water and have it lab-tested. This will let you know if the water is safe for your fish. 


Rainwater may seem very clean and safe for use as aquarium water but it is sometimes not. This is because pollutants in the air usually get mixed with it and this could result in the water being acidic in some cases.

Thus, if you regularly collect rainwater, before using it for your aquarium, you should take a sample for testing to establish the pH and mineral content. Establishing these two things will let you know if the water is safe for your fish tank.


You cannot use most bottled water brands to fill your aquarium. This is because most of them may be clean but they are in one way or the other not safe for fish. Using bottled water to fill your fish tank will also be expensive in the long run. The cheapest and most convenient water to use to fill your fish tank is tap water.

However, add a water conditioner to it or let it sit first to remove chlorine from it before using it for your aquarium. This will make it safe for your fish.