Should You Let Water Sit Before Adding Your Betta?

Betta fish, like all fish, are sensitive to the chemicals we add to water to make it safe for human consumption. Specifically, and in a general system, those chemicals are chlorine and chloramine.

Fortunately, both of these chemicals tend to dissipate into the atmosphere when you leave water to sit for a while. So, if you’re using tap water, yes you need to let the water sit for at least 24 hours. That’s the short answer.

There’s a lot more to consider, though. In this article, we’ll take you through the long answer, discussing different factors like:

  • How different types of water affect your betta fish
  • Using water conditioners and dechlorinators
  • Whether or not aged water is better for your betta.

Betta Fish and Their Water Needs

Betta fish, or Siamese fighting fish, are beautiful tropical fish. They’re hardy enough, but highly sensitive to certain toxins. That’s why you can’t toss them into a bowl of water and leave them to fend for themselves.

They make ideal pets, but as with any pet, caring for betta fish requires forethought and planning, including water preparation. Before you jump in and let a bucket of water sit for 24 hours, there are a few things to consider though.

Most specifically, what kind of water are you using?

How Water Type Affects Betta Fish

If you take the time to think about it, you know that all water isn’t equal. You don’t want to drink sea water, or the water that gathers at the side of the road. In the same way, your betta is highly sensitive to the type of water you use.

Ignoring issues like pH level, water hardness, and water temperature for the moment, the type of water you use is essential. In most cases, aquarists have access to one of four types of water:

  • Tap Water – By far the most common type of water, tap water is heavily treated with chemicals and antibacterial agents. Before using it for bettas, it needs to stand for at least 24 hours to allow chemicals to evaporate or dissipate. You may also use water conditioners or dechlorinators, but we’ll discuss those later.
  • Spring Water – Some aquarists swear by spring water for their tanks, and use nothing else. Unfortunately, over recent years, we’ve seen many scandals where companies substituted tap water for spring water, or the springs became contaminated. We’d suggest letting it sit, or using a water conditioner.
  • Reverse Osmosis WaterReverse osmosis, or RO, water is some of the cleanest water you can find. It runs through a filter that contains a series of microscopic membranes, which remove even the tiniest of contaminants. You don’t need to treat it in any way before using it.
  • Well or Borehole Water – In some cases, aquarists have access to groundwater, in the form of a well or borehole. If the water source has been tested and rated safe for consumption, you can generally use that water for your aquarium without prior treatment.

Once you know what type of water you’re using, you need to decide if you’re using a water conditioner or dechlorinating agent.

Water Conditioners and Dechlorinators

If you’re using tap water or spring water, you have two options. Either you wait at least 24 hours before adding your betta fish to your tank, or you use a water conditioner or dechlorinator. 

Water conditioners may be dechlorinators as well, or they may only be conditioners. If you’re going to be using one to replace the waiting time, you need one that serves both purposes, or you need a conditioner and a dechlorinator.

A water conditioner helps prepare the water, adding beneficial bacteria and elements that will help your betta fish thrive. A dechlorinator will remove the chlorine and chloramine from the water. Most dechlorinators only take between five and 15 minutes to completely remove the toxic chemicals from the water.

If you’re using both a dechlorinator and water conditioner, use the dechlorinator first then add the conditioner ten to 15 minutes later.

How Long Should I Wait to Put My Betta Fish in New Water?

The short answer is, you shouldn’t. While betta fish require clean water, you shouldn’t ever put them through the stress of changing all their water at once. Instead, it’s a good idea to practice betta water changes. 

Although betta fish have labyrinth organs, allowing them to breathe atmospheric air, they still benefit from good filtration and heating. You should have them in a well-seasoned aquarium which has had chance to cycle before you bring the fish home.

After that, you should exchange about a quarter of the water once a week. Once a month, or every fourth week, you should exchange half the water. Always allow the water to sit, if you’re using tap or spring water, or use a dechlorinator.

Add the new water slowly over a few hours, in small amounts, so that the tank has chance to reach a new equilibrium before you add the next portion of water.  

Should I Let Water Sit before Adding to Fish Tank?

Whenever you add new water to the aquarium, you should either let it sit or treat it. As mentioned before, if you’re using RO water or well water, this step is unnecessary. 

If possible, it’s a good idea to have a spare heater so you can bring the new water to the same temperature before adding it. 

Some people might tell you that, as long as you don’t change more than 30% of the water at any time, you don’t have to treat the new water or let it sit. If you’re using tap water, this simply isn’s true. 

While the chlorine will be diluted to some degree, your betta fish can still become sick from the trace toxins. Additionally, the toxins may kill the beneficial bacteria that you worked so hard to cultivate.

How Long After Treating Water Can You Add Betta Fish?

You can add the water to your betta tank, ten to 15 minutes after treating it. Always add the conditioner to the new water and allow it to reach full efficacy before adding the new water to your aquarium. If you purchase your betta fish from a pet shop, they may give you a bottle of water conditioner with your betta. If not, buy a bottle.

Can You Put Betta Fish in Water Right Away?

As mentioned above, it depends on the type of water. With well water or RO water, yes you can. With tap water or spring water, not unless it’s a choice between life and death for your fish at that moment (like if your aquarium broke). 

In case you do have to make a split second decision, ensure that you always have dechlorinator and water conditioner on hand and add some to the water immediately. If you’re lucky, your betta fish will make a full recovery from its exposure to toxins. 


If you’re using tap water, you should let it sit for 24 hours before adding it to your betta fish tank, or placing your betta in it. Alternatively, you can use water conditioners and dechlorinator to create optimum betta water conditions within 15 minutes.

Fortunately, it’s an easy process, and one you can avoid entirely by using water filtered through reverse osmosis. Small RO systems are becoming more affordable, and you can easily get one to filter tap water at home! If you’re getting ready to bring home your first betta fish, check out our article about acclimating your betta fish.

If you have any questions we haven’t answered above, feel free to contact us and tell us what else you’d like to know about water conditioning for your betta fish.

If you want to learn more about Betta’s behavior, advice, and tips, please visit our collection of Betta Tips Articles.

About the author

Hi, I am Alex.
My passion is aquariums. I am especially drawn to betta fish. I love experimenting, learning, researching, and writing about them.

You can find the articles I wrote here

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