Will Cloudy Water Hurt Your Fish? (& What To Do About It)

Cloudy water in your aquarium can be harmful to your fish, making them unhappy, stressed, and even sick. Cloudy water can appear in different ways, and it can be the result of various factors that are important to try and either prevent or handle when you notice the cloudiness building. 

In this article, you’ll learn everything about cloudy water and what to do about it. So, keep reading!

Key Takeaways:

  • Cloudy water in an aquarium might signal issues with water quality, potentially impacting the health and happiness of fish.
  • Factors leading to cloudy water include initial aquarium setup, the presence of nitrating bacteria, unsuitable water choices, and inadequate cleaning of accessories or plants.
  • Cloudiness after a water change, overstocking the tank, and excessive algae growth can also contribute to cloudy water.
  • Persistent cloudy water, if not addressed, can harm fish, potentially leading to illness or even death.
  • The duration fish can live in cloudy water depends on the cause; cloudy water during cycling or due to good bacterial activity isn’t harmful.

Why Is My Aquarium Water Cloudy? 

It’s not unlikely that, at first sight of cloudy aquarium water, you’ll likely be concerned that something is wrong. However, it’s important to analyze a few factors to determine what caused the cloudiness, as there are some instances where cloudy water is completely normal. 

Causes of Cloudy WaterPotential Harm to FishSolutions
Initial aquarium setupImpact on health and happinessAllow time for settling
Nitrating bacteria presencePotential illness or deathWait before introducing fish
Unsuitable water choicesAltered water compositionUse water conditioner
Aquarium accessoriesPossible impact on fishMonitor water quality
Algae presenceDisruptive to fish healthRegulate and treat algae growth
Water change aftermathTransient cloudinessObserve fish adaptation
Overstocking the tankBacterial imbalanceAvoid overstocking, maintain balance
Bacterial bloomPart of healthy setupLet the process complete
Oxygen limitationImpact on fish behaviorTest and clean water
Fish tolerance to cloudinessVaried effects based on causeEnsure a healthy environment
Green cloudy waterAlgae overgrowthTreat algae and prevent recurrences
Persistent cloudy waterPotential harm over timeIdentify and address the cause

Your Aquarium Was Just Set Up 

When people are putting together their aquariums for the first time, there is the potential that the water will appear cloudy until you’ve finished setting it up. Aquariums are more complex in their setup requirements than just adding water, decorations, and then fish. 

As you continue to build up your aquarium in preparation for fish, you shouldn’t be surprised if you see some cloudy water. A lot of chemistry is occurring in the tank, and as long as the cloudiness dissipates in a couple of days, your aquarium should be fine. 

Nitrating Bacteria Is Present 

As mentioned, when you first set up an aquarium, it’s normal to see cloudy water in the first few days. This is because there are nitrating bacteria present, which helps to eliminate many of the common contaminants in water that are not ideal for aquatic life. It’s important to let this process happen before you slowly start integrating fish into the aquarium. 

Your Water Choice Is Subpar

Some types of fish will have specific requirements for what kind of water they can live in. For example, some fish thrive when living in distilled water or freshwater. When you fill-up an aquarium with tap water, it can appear cloudy due to all the minerals present in it. 

Since many of these minerals can be toxic to fish, you need to use a conditioner in the water to remove these substances. 

Your Aquarium Accessories Are Changing The Water

Even if you purchase aquatic-safe accessories for your aquarium, some of them need rinsing to be prepared for water usage. One example of this is driftwood. Some accessories or plants can release things into the water, which can alter the cloudiness and overall composition of the water, which may impact your fish. 

As long as you monitor water quality and the presence of potential contaminants, your fish should still be safe. 

Male hand cleaning aquarium using magnetic cleaner.

There’s Algae In Your Aquarium 

The presence of algae is likely to be in any aquarium, but when algae are able to spawn out of control due to poor aquarium conditions, it can end up being harmful and disruptive to your fish’s health and happiness. 

You’ve Just Completed A Water Change 

Water changes are a very important component in keeping water appropriately conditioned for your fish. However, doing this could result in the water becoming cloudy once again for a couple of days. Just be patient, test your water, and monitor how your fish are adapting to the water change. 

There Are Too Many Fish In The Aquarium 

When you add more fish to an aquarium than you should, it can lead to a number of issues. You might end up with unruly or stressed fish because they don’t have enough space. You also run the risk of water becoming cloudy due to an excess of waste and food contaminants staying in the water and building up. 

When this occurs, it can cause bad bacteria to build up so quickly that the good bacteria present in the water can’t take care of it quickly enough. This can lead to all sorts of poor consequences for your fish, such as disease and stress, which can all have fatal impacts. 

Will Cloudy Water Hurt Your Fish?

There is a potential that the cause of your cloudy water could hurt your fish. As such, it’s important to know the signs that cloudy water is potentially harmful so you can mitigate the risk as soon as possible. 

Bacterial Bloom Is Good For Fish

Bacterial bloom is the proper name for the process that occurs when you set up a new tank, and the good bacteria is eliminating the unwanted bacteria and minerals. You need to allow this process to happen before you introduce fish into the tank. If the cloudiness is still clearing up while you introduce fish to the tank, it’s not going to harm them. 

Some Cloudiness Can Limit Oxygen Supply 

You should be cognizant of your fish and their behavior, such as if they appear to be gravitating toward the top of the tank. They might do this in an effort to get more oxygen because it’s not present enough in the water. This is a good sign that your water needs to be tested and cleaned. 

Some Fish Aren’t Bothered By Cloudiness

Some fish won’t mind if their water is cloudy, especially if it’s not caused by an excess of harmful bacteria. This is because it mimics the conditions of their natural environment, where water was murky, to begin with. 

Be Wary Of Cloudy Green Water 

As mentioned, the presence of green and cloudy water could be an indication that there is an abundance of algae present in your aquarium, which can end up being a detriment to your fish’s health. Thankfully, there are ways to treat the algae problem and avoid it occurring again, but it will take some work on your end. 

Persistent Cloudy Water Could Be Harmful  

If cloudy water is just left to persist, it could potentially lead to your fish getting hurt. This is because if cloudy water doesn’t naturally clear up on its own, it’s a good sign that something unsavory is occurring in the water, which will, in turn, lead to your fish getting sick if it’s not dealt with. 

How Long Do Fish Live In Cloudy Water?

There’s no definitive answer as to how long fish can live in cloudy water. It’s all going to depend on the reason why the water is cloudy and how long you allow the water to remain cloudy before determining the root cause of the condition. As mentioned, cloudy water at the initial setup of an aquarium is to be expected.

It’s also normal for some cloudiness to occur after you’ve cleaned the water or completed a water change. Cloudiness means that good bacteria are interacting with bad bacteria to eliminate them, which will actually increase the overall quality and duration of life for your fish compared to how dirty water would shorten it. 

Cloudy water that is due to algae buildup or excess waste is the most concerning in terms of how it can impact the lifespan of fish. All kinds of contaminants can build up and fester, such as carbon dioxide, ammonia, and phosphates. Without taking care of these matters, fish can become ill and could end up passing away within days or weeks. 

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What Should I Do If My Fish Tank Water Is Cloudy?

You can likely prevent cloudy water in many cases by learning and implementing the right tools to maintain a healthy aquarium. However, aquarium enthusiasts know that, no matter how careful you are, things can happen. As such, there are some tools you can use to deal with cloudy water if it occurs. 

Test Water For Contaminants 

You should be regularly testing your aquarium for contaminants such as ammonia, nitrates, and phosphates. These contaminants are not good for your fish, and thus, it’s important to monitor water quality and take care of the situation when it arises. 

Complete A Water Change 

Water changes are also meant to be a regular part of aquarium maintenance. Doing this appropriately and properly based on your specific aquarium setup is crucial to help clear the quality of your water. That said, cloudiness will not go away right away, so be patient. 

Add Activated Carbon To Your Aquarium 

Activated carbon comes in a few different forms that can be used in aquariums. What this does is break down a lot of the contaminants in water that can cause cloudy water and other unsavory water conditions. 

Introduce Gravel From A Healthy Fish Tank

You won’t be able to do this unless you have more than one aquarium in your home. However, if this is a possibility, you can take some of the gravel in your healthy aquarium and put it in your cloudy one. This can help because it helps to introduce more healthy bacteria into the aquarium needed to clear up the water. 

Check The Filter

Filters help to keep bacteria and contaminants out of water in collaboration with natural processes and filtration from aquatic plants. It’s important to keep your filter clean and to make sure the size of your filter is appropriate for your aquarium. If not, it may be worth investing in a larger filter. 

Clean And Replace Gravel 

A lot of excess food and fish excrement can fall to the bottom of the tank, making home inside the gravel or substrate at the bottom. This can lead to all sorts of nasty bacteria breeding in the water. Be sure you occasionally clean up any old gravel and replace it with some fresh gravel occasionally, being sure to rinse your gravel before putting it into the aquarium. 

Now, check out this video by KeepingFishSimple on how to fix cloudy water in your tank the easy way!

How To Avoid Cloudy Water In Your Tank

The nice thing is, if you have done your research before acquiring an aquarium in terms of how to maintain it, you are already doing many of the things necessary to avoid cloudy water. Beyond maintenance, there are some ways to avoid cloudy water during the setup of your aquarium and afterward. 

Cycle Your Aquarium Appropriately 

There’s a cycling process that needs to be done for every new aquarium in order to safely prepare fish to live inside of it. This process involves a series of steps that takes about four to six weeks to complete. 

It is possible to see some cloudiness in your aquarium during setup, but it should clear up a couple of days after you’ve completed the cycling process. Being sure to cycle your aquarium can aid in the process of preventing unsavory cloudiness. 

Do Water Changes Appropriately

Water changes are important because they help you take some of that dirty water out of the tank to replace it with clean water. It’s not recommended you use tap water, but if you have to, be sure to put it through a water filter and use a water conditioner before adding it to a tank. 

Additionally, you want to only change about 25% of the water at a time and try to pour water in when it’s around the same temperature as the aquarium water. This will help avoid as much shock to your fish as possible when introducing new water. 

Choose The Right Substrate 

The substrate can be one of the most common causes of cloudy water. While it’s not meant to cloud up your water, some types of substrate do not contain the epoxy coating to avoid making your water appear dull. If you choose a substrate with no epoxy coating, be sure you rinse it thoroughly before placing it into your aquarium. 

Learn About Aquatic Accessories And Plants

It’s important to do some quick research or ask questions before adding accessories, toys, and plants to your aquarium. Not only do you need to know if your choices are right for the type of fish you want, but you need to know if you have to anchor something or rinse it so it doesn’t distort the water. 

Don’t Overcrowd Your Aquarium 

Having too many fish in your aquarium could lead to an increase in the amount of waste in the aquarium, tons of food crumbs, and potential stress for your fish. This can contribute to cloudy water due to unsanitary conditions. 

Do Not Overfeed Your Fish 

Overfeeding doesn’t automatically mean your fish will eat too much, though it’s likely that they will depend on the type of fish you have. However, what will happen is that there’ll be too much food waste and excrement in the fish tank, and the positive bacteria within the water won’t be able to break that down and get rid of it quickly enough. 

It can be difficult to avoid overfeeding fish, as instructions for feeding provided on packaging can be misleading. Instead, it’s best to learn the specific eating habits of your fish based on breed and observable behavior, so you can feed them the appropriate amounts, reducing food waste. 

Frequently Asked Questions

Keeping your aquarium water clear and clean is often a priority for many aquarium owners, but the biggest priority is doing so in a way that is safe for the health of your fish. 

Can I Add Water Conditioner While The Fish Are In The Tank?

You can use a small amount of water conditioner while fish are in a tank, but you have to be very careful about how much you use. It’s ideal that you read product instructions, so you avoid putting too much conditioner in the tank, thus making your fish very ill. 

A water conditioner is an important product for aquariums, as it helps to mitigate any chlorine from building up in your tank, which can be deadly for your fish. That said, putting too much water conditioner in when fish are already living in the aquarium can also be deadly. 

How Do I Make My Fish Tank Water Crystal Clear?

Making your aquarium water as crystal clear as possible is relatively easy. Part of this process includes maintaining the integrity of your aquarium through testing water, conducting proper water changes, and having a proper, well-functioning filter. 

You also want to ensure that nothing negative is able to grow in your tank. There are also products available, such as water clarifiers, that will assist you in making your water look fresh and clear. 

How Long Can Fish Survive in Cloudy Water?

The survival time of fish in cloudy water can vary depending on the species, water size, and level of cloudiness. Cloudy water can reduce oxygen levels, and affect food finding and predator avoidance. It’s important to monitor water quality and take measures to ensure a healthy environment for fish to thrive.


Cloudy water isn’t going to harm your fish in every instance. This is especially true if your aquarium setup is in its infancy. However, it’s important to pay close attention when you’ve already had your aquarium up with the fish present and the water becomes cloudy. 

If you have implemented proper aquarium maintenance protocols into your routine, you’ll likely be able to avoid many of the issues that cause water to become cloudy. It’s crucial that you address the cloudiness through these protocols in case it’s caused by something that can end up making your fish very sick in the future. 

When you do so, you’ll keep your water looking fresh and clear so you can watch your fish swim around happily.



About the author

Hey there! I'm Antonio, the passionate owner and chief editor of Betta Care Fish Guide. With over half a decade of hands-on experience, I've become your go-to expert for all things betta and tropical fish.

Over the past 5 years, I've not only kept bettas and other tropical fish but also connected with a diverse network of hobbyists, seasoned fishkeepers, and even veterinarians.

Now, I want to help other beginner fish keepers who had the same questions as me when they were just starting out! So they can save themselves a ton of time and keep their fish happy and healthy!