How to Use Tap Water for a Betta Fish Aquarium

How To Use Tap Water for a Betta Fish Aquarium: Our Guide

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If you put tap water directly into your betta fish tank, your poor pet will die pretty quickly!

How so? Well, untreated tap water contains chemicals that are extremely toxic to fish.

Fortunately, making tap water safe for your betta’s tank is pretty straightforward. The easiest way to do that is by adding a special de-chlorinator to the water before adding the water to your tank.

In this guide, we explain how you can treat tap water to make it safe for your betta’s tank.

Key Takeaways

  • Tap Water Toxicity: Directly adding tap water to a betta tank without treatment can be fatal due to the chlorine and chloramine it contains.
  • Simple Dechlorination: De-chlorinators effectively neutralize harmful chemicals, making tap water safe for betta fish aquariums, so adding a de-chlorinator is the most straightforward method to make tap water betta-safe.
  • Routine Water Management: Implement a schedule for changing 10%-30% of the tank water every week to ensure a clean habitat for your betta.

How Long Can a Betta Fish Live In Untreated Tap Water?

You should never put your betta fish in a tank that contains untreated tap water!

Bettas can sometimes survive for a few days in untreated tap water. However, in an uncycled tank full of tap water, the fish most likely won’t last more than 24 hours.

Why Do You Need To Treat Tap Water?

So, why do you need to treat tap water before adding it to your betta’s tank?

We use tap water for drinking, food preparation, and washing. Your local water treatment company adds certain chemicals to the domestic water supply to kill harmful bacteria that would otherwise make you sick if you drank the water.

Those chemicals include chlorine and chloramine, both of which are highly toxic to fish and other aquatic life.

In addition, chlorine and chloramine will kill the beneficial bacteria that your tank and biological filter system contain, leading to poor water quality and a toxic environment for your fish and other livestock.

Also, chlorine and chloramine can affect the pH levels and salinity of the water.

Bottom line: Before you add any tap water to your betta’s aquarium, you must ensure that all the potentially harmful chemicals are neutralized or removed by de-chlorinating the water.

How Often Should You Change a Betta’s Water?

Ideally, you should carry out small partial water changes of 10% to 20% per week. However, if you have a large betta tank, you can change 20% to 30% of the water every two to three weeks.

Use of Chlorine and Chloramine

According to the Safe Drinking Water Act (SDWA) of 1974, it’s legally required by the Environmental Protection Agency that all domestic water supplies are treated with chemicals.

This will ensure that the water is free from contaminants and harmful bacteria so that the water is safe for the public to drink and use.

Until recently, chlorine was generally used by most water companies to treat your tap water. However, most water treatment plants now use chloramine instead. That sounds pretty straightforward; however, it’s not that simple.

Do you sometimes notice that your tap water tastes or smells more “chemically” than usual? Well, that’s because water treatment companies vary the levels of chemicals they use. The companies measure coliform levels in the water.

Once a certain level is reached, the water is bombarded with higher levels of chlorine and chloramine. So, on some days, chemical levels will be relatively low, whereas, on others, the levels will be super-high.

However, generally, the levels of chloramine and chlorine in tap water are between 0.5 and 2.0 ppm (parts per million.)

What Is Chlorine?

Chlorine gas is used to kill dangerous bacteria that might find their way into the public water supply.

Water that contains chlorine can be made safe for use in fish tanks through a process called “gassing off.” All you do is allow the water to stand for 24 hours, stirring it occasionally to encourage the chlorine gas to evaporate.

When I first got into the fishkeeping hobby over 40 years ago, there was no such thing as a de-chlorinator product for use in aquariums. The only way to make tap water safe was to use the method described above. That was not only very time-consuming but had an element of risk, as sometimes not all the chlorine would be removed, posing a danger to your fish.

I routinely used rainwater from my parents’ water butt mixed with tap water to top up my fish tanks, which worked pretty well.

However, these days, most water companies use chloramine rather than chlorine, which presents a problem I never had to deal with back in the day.

What Is Chloramine?

Chloramine is also known as monochlorine. Water companies use chloramine because it doesn’t evaporate as easily as chlorine and is more stable.

However, chloramine contains a lethal cocktail of chlorine and ammonia, which is deadly to fish. And the gassing-off method of making tap water safe doesn’t work with chloramine.

Why Are Chlorine and Chloramine Dangerous to Bettas?

Chlorine and chloramine are hazardous to betta fish.

But why?

Chemical Burns

Chlorine causes chemical burns to the gills and internal organs of invertebrates and fish, even at low levels.

A betta fish suffering from chlorine poisoning will become extremely stressed thanks to the constant pain the burning causes.

Some fish develop hyperemia or redness on parts of their body, gasp at the water surface desperately trying to breathe through their inflamed gills, and swim erratically because of the neurological damage the chemical causes.

Does Your Tap Water Contain Chlorine or Chloramine?

So, how do you know if your tap water contains chlorine or chloramine?

Well, the easiest thing to do is to speak to your local domestic water supply company and ask them. You can also use an aquarium water test kit.

A good aquarium water testing kit will tell you whether your tap water contains ammonia. If the water contains chloramine, it will test positive for ammonia.

Once you know what your tap water contains, you can choose the right treatment product to make it safe for your betta.

How To Treat Tap Water for Betta Fish

There are several ways of making tap water safe for betta fish:


These days, the easiest and most effective way to rid your tap water of dangerous chemicals is to use a chemical de-chlorinator, such as API Tap Water Conditioner.

API TAP WATER CONDITIONER Aquarium Water Conditioner 16-Ounce Bottle
  • Contains one (1) API TAP WATER CONDITIONER Aquarium Water Conditioner 16-Ounce Bottle
  • Neutralizes chlorine, chloramines and other chemicals to make tap water safe for fish
  • Prevents tap water chemicals from causing gill destruction, tissue irritation and fish death

However, you should know that not every de-chlorinator can deal with chloramine, so remember to check the label before you make a choice.

Dechlorinators are formulated with a chemical called sodium thiosulfate that turns the chlorine into chloride ions, which are harmless to your fish. However, if the water contains chloramine, the ammonia element of the chemical will still be in the water.

So, you must double-check that your chosen product works on chloramine as well as chlorine.

How Long Does It Take To Dechlorinate Water for Fish?

Once you’ve added a de-chlorinator to a bucket of tap water, you only need to wait a minute or so before it’s safe to put the water into your betta’s tank.

Alternative Water Treatment Methods

Aside from dechlorinators, there are several other methods that you can use to remove chlorine and chloramine from tap water, rendering the water safe for use in your betta’s tank.

Ultraviolet Light

UV light destroys chlorine and chloramine in tap water. Some homes have a special unit installed in their homes as part of a dechlorination system, which could be an option for you.

Ascorbic Acid and Sodium Ascorbate

Ascorbic acid and sodium ascorbate are two forms of vitamin C that are highly effective at removing chlorine and chloramine from tap water, according to the U.S. Department of Agriculture Forest Service.

Activated Carbon

Thanks to a catalytic reduction reaction, activated carbon can remove chlorine and chloramine from tap water. However, even if you use activated carbon in your tank’s filter media, you’ll still need to treat tap water before using it to top up your tank.

Campden Tablets

Betta keepers who brew their beer will have heard of Campden tablets. Campden tablets are used to sterilize wine, cider, and beer and to retard wild yeast growth.

Chlorine and chloramine can make the brew taste unpleasant, so homebrewers use Campden tablets to get rid of the chemicals from the water.

Simply add one Campden tablet per 20 gallons of tap water, let the water rest for 20 minutes or so, and the chloramine and chlorine will be gone!

Home Chloramine Filters

In some areas, levels of chloramine in tap water are pretty high, making the water taste unpleasant, so many homeowners invest in a home carbon water system.

The system fits onto faucets and showerheads, removing the chlorine content of the chloramine molecules and taking the ammonia that’s left through reverse osmosis or via a cation filter.

Unfortunately, at $15,000, these systems are pretty pricey to install, and maintenance costs are high too.

Can You Use Well Water for Betta Fish?

How to Use Tap Water for a Betta Fish Aquarium

In theory, you can use well water for your betta fish tank. However, well water can contain heavy metals, chlorine, and chloramine, so we recommend that you treat the water with a de-chlorinator before adding it to your tank.

What Other Chemicals Are Contained in Tap Water?

Tap water also contains some common inorganic chemicals, including nitrates, nitrites, copper, fluoride, and phosphates. Typical tap water sources contain up to one ppm of these chemicals.

You will most likely find nitrate levels up to 10 ppm. The typically low levels of both nitrites and nitrates pre-existing in tap water can be easily removed with a de-chlorinator. Also, having a good biofilter in place will greatly aid the removal of these contaminants.

Nitrites and Nitrates

Although most betta owners spend much of their time worrying about nitrate and nitrite levels in their betta’s water, the levels of these chemicals contained in tap water are so small that they won’t harm your fish, provided you stick to a correct tank maintenance routine.

Other Chemicals Found in Tap Water

There are some other “allowed chemicals” in tap water that are worth mentioning.

Copper is commonly found at around 1.3 ppm. Fluoride can be found at around 4 ppm. Phosphates are also common in tap water.


Although these low copper levels don’t cause a problem for your betta, it’s good to take note of that because there are times when you might need to treat your aquarium with a medication containing copper sulfate.

Suppose the medicine you’re using to treat a condition in your aquarium calls for exact measurements of copper. In that case, it’s important to know the baseline of the pre-existing copper content that might be in your tank water.

One other side note about copper content in tap water is that if your home has copper plumbing, you will have naturally occurring copper in the water straight from your tap. Copper levels at or above 25 ppm can cause harm to most species of fish and invertebrates.


Many cities and towns add phosphates to their water supply because phosphates can reduce lead that’s commonly found in drinking water.

The problem with phosphates in aquarium water is that they tend to exacerbate algae growth, especially blue-green algae, which isn’t great news for aquarium keepers.

Total Dissolved Solids

Salts, metals, and minerals that are dissolved in water make up the TDS or total dissolved solids category in tap water. Anything in water other than pure H2O could fall in this category, including suspended solids.

Substances that are neither dissolved nor settled in the water are considered suspended solids. Total dissolved solids are generally measured in parts per million, which is the way-to-weight ratio of an ion to water.

Reverse osmosis systems can drastically lower the total dissolved solids from tap water sources. Remember that reverse osmosis is also capable of removing even trace amounts of minerals from the water.

Sodium in Tap Water

The EPA (Environmental Protection Agency) states that 20 mg or less of sodium per liter is the perfect amount to have in everyday drinking water.

Generally speaking, a higher level than this suggestion will end up chasing out certain specific minerals that fish find essential for their general well-being.

Calcium and magnesium are two of the more important minerals that high sodium levels will chase away.

Levels over 270 mg/L in freshwater would generally be regarded as very high. Maintaining the correct amount of minerals at this level of sodium would be beyond difficult in maintaining a healthy aquarium.

If you haven’t put it together yet, this is all being stated as proof of why you shouldn’t ever use water that’s been passed through a water softener (that uses salt to soften the water) for use in any type of aquarium.

Bottled Water

It should be noted that most bottled water shouldn’t be used to fill up your betta’s aquarium.

More often than not, drinking water is passed through a reverse osmosis system, having the minerals stripped from it and then adding choice minerals back into it just to accommodate the pallet. Distilled water, of course, doesn’t have any minerals in it at all.

If you can find a bottle of water that is labeled “spring water,” and you know for a fact it came and was sourced from a spring, that kind of water is generally okay for use in an aquarium.

What About Tank Decorations and Plants?

You might wonder whether you should rinse new tank decorations in untreated tap water. I routinely wash all new decorations in tap water before adding them to my setups. However, when cleaning existing decor, I use old tank water to protect the beneficial bacteria that might be living on the decorations, which would be killed off by the chlorine and chloramine in tap water.

I recommend you take a look at this thread on Reddit, where old and new betta fans discuss their water treatment ideas. There are some very interesting ideas here!

Final Thoughts

I hope you enjoyed our guide on how to treat tap water for betta fish. If you did, please take a moment to share the article.

In a nutshell, the easiest way to remove harmful chlorine, chloramine, and other chemicals from tap water before adding it to your betta tank is to treat the water with a de-chlorinator that you’ll find in your local fish or pet store.

Happy betta keeping!

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