Betta Fish Cloudy Water: Causes And Treatment Of Dirty Aqua

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Last Updated: September 29, 2023 by Flora Gibbins

When keeping a Betta fish, one of the things you’ll run into eventually is a cloudy tank. However, as terrifying as it is to lose sight of your Betta in suddenly murky waters, there’s no need to panic. 


You can easily remedy the situation by understanding the underlying causes and doing detective work.

We’ll reveal what causes the “Betta fish in cloudy water” phenomenon and remedies to the situation in this article, so keep reading to make your Betta’s tank water crystal clear.

Identifying a Case of Cloudy Tank Water 

Below are the unmistakable signs to watch for when identifying whether you have a cloudy fish tank on your hands:



Usually, cloudy water is either white, gray, or green. The color you see in your Betta tank will depend on the underlying cause and determine the type of treatment necessary to fix the issue.

Level of Opacity 

Level of Opacity 

Additionally, how well you can see through the water in your fish tank varies. On some occasions, the fog is so thick that you don’t know what’s going on inside the tank, which can be extremely worrying. In other instances, you can see just fine; however, that offers cold comfort.

Disappearing and Reappearing 

Disappearing and Reappearing

The cloudiness in your Betta tank water may appear and disappear very quickly. One moment, the water is crystal clear; the next, it’s murky and shrouded in an impenetrable fog.

Underlying Causes of Cloudy Aquarium Water

Once you can identify tell-tale signs of a cloudy fish tank, the next step would be to find out what’s causing the issue. While it’s true that not every factor causing cloudy water will be within your control, you aren’t entirely powerless in the options you have to remedy the situation. So let’s take each symptom one at a time.

Gray or White Cloudy Water

It’s more common to stumble upon gray or white cloudy water than to see murky green water. Here are some possible causes of the issue:

Bacterial Bloom

Bacterial Bloom

When bacteria grow in fish tanks, they can cause the water to get murky. However, you’d be surprised to know that it isn’t necessarily harmful bacteria that make a fish tank cloudy; a surge in beneficial bacteria found on live plants may also be behind the cloudy water.

Water Quality

Water Quality

Sometimes, a change in water parameters over time may cause cloudy aquarium water. Usually, it signifies that the bacterium population in the tank is growing, with the result being gray or white cloudiness.

Gravel Conditions

Gravel Conditions

When you add gravel to a new fish tank, and the water becomes cloudy, it’s most likely due to poorly cleaned gravel. You can clean your gravel correctly by washing it with water and using a water conditioner.

However, the issue isn’t limited to newly-added gravel, as moving old gravel in an established tank may result in the same gray or white cloudiness. For example, you might cause this to happen when using a gravel vacuum to clean the tank bed. This is because the disturbed gravel will free up built-up sediment in old tanks, releasing it into the water.

Green Cloudy Water

Algae growth is the number one cause of cloudy water in a fish tank with a greenish tinge. Here are some of the factors that make algae thrive in tank water.

High Level of Phosphates

High Level of Phosphates

Phosphates contain excess nutrients that aid algal growth. They can appear in your tank in many ways, mainly through decaying, uneaten food or dead fish or fish fry.



If there’s one thing algae love, it’s light. Therefore, expect them to blossom if the aquarium light in your tank is too bright. Additionally, a tank positioned near a window where direct sunlight gets through or in a room with very bright lights won’t fare any better. 

To summarize, an environment with too much light is a haven for algae.

Other Hues

Cloudy water may also appear yellowish. Let’s look at the factors responsible for this color:



Adding decorations like driftwood to your Betta’s tank will help to keep the fish from getting bored. However, it may also have the side effect of introducing tannins into the tank water. The tannins cause the water to appear tea-like in color, giving your tank a sickly look.

Hard Water

Hard Water

When you perform water changes, it’s possible the water you put into your tank may be too hard and contains metals and other minerals. This will make the tank’s water appear foggy. You’ll need to get your aquarium water tested to ensure it isn’t too hard.

The Tank’s Glass

The Tank's Glass

Sometimes, it might not be a problem in the water that’s causing its cloudy appearance but a problem with the tank. For example, bacterial biofilm is known to grow on aquarium glass, causing it to appear cloudy to an outsider looking in.

How to Treat Cloudy Water

You can restore the water in your tank to pristine condition reasonably quickly. Below are some of the things you can do:

1. Turn the Lights Down

Turning down the lights in your aquarium or room will help curb algal growth, the leading cause of green cloudy water. You could also try covering your tank with some cloth or paper every now and then to keep light from getting in. Additionally, ensure your tank isn’t too close to a source of sunlight like a window.

2. Add Beneficial Nitrifying Bacteria

You can introduce more beneficial bacteria into your tank in one of two ways: either purchase some bacteria culture or add a biological sponge from another filter. Adding these bacteria will help to restore balance in the tank.

3. Minimize the Number of Fish

Try not to add too many fish to your tank. An inch of fish per gallon of water is a good yardstick for populating a new tank. Tropical fish have more space to swim around in the wild and aren’t confined in a small tank. If you must have a tank full of fish, consider buying a larger tank.

This way, you’ll emulate your pet’s natural environment. On that note, a 5-gallon tank or larger is the only suitable size for housing Betta fish.

4. Filter Maintenance

“Will a filter clear cloudy water?” is a question commonly asked, and aquarium owners and fish keepers alike are divided on the answer.

Regularly cleaning your filter media should help rid your tank of bacteria (the bad ones) and the buildup of other microscopic nasties. But it may also rid your tank of beneficial bacteria that help your tank’s nitrogen cycle.

However, since you can always add beneficial bacteria back to a tank, we don’t think cleaning the filter should pose a problem.

5. Don’t Overfeed

Overfeeding your Betta fish will cause bacteria to bloom in the tank, making the water cloudy. Moreover, it may prove dangerous because any excess food not consumed by your fish will be broken down by these bacteria, significantly raising the ammonia and nitrite levels in the tank.

6. Change the Water Regularly

Regular water changes will help restore water parameter balance in the entire tank. A 10-15% water change is a great starting point, depending on the size of your tank. Bigger tanks may be OK with a 5-10% change, while goldfish tanks may require a 50-80% change.

In terms of how often, change your tank water at least once per week. Keeping track of the nitrate levels is an excellent way to do this, and you want to aim for a tank with water that contains 20 ppm nitrates or lower.

7. Vacuum Regularly

Using a gravel vacuum to clean the gravel bed in your tank will help remove fish waste, uneaten food, and other things that may decay in the gravel and cause bacteria to thrive unabated. 

Gravel vacuuming will also help keep the ammonia and nitrite levels in the tank down to a minimum.

However, as mentioned earlier, it may free up sediment in old tanks, so keep that in mind.

8. Boil the Driftwood

Boiling driftwood before adding it to your Betta’s tank will help to keep it from introducing tannins into the water. You can also try soaking the driftwood for several days to prevent it from leaching tannins.

9. Check for Dead Fish

If you keep more than one fish in the tank, check to see if they’re all accounted for. A dead fish may be responsible for the tank’s cloudiness. Dead fish incidents are more likely to occur when you keep fish with different lifespans in the same tank.

10. Do Nothing

You also have the option of waiting for the problem to clear up. Sometimes, cloudiness could be gone on its own, so you might not need to do anything unless the problem persists for more than a few weeks.

However, if the cause of the cloudiness is apparent (for example, cloudiness caused by algae), don’t hesitate to fix things.

Fun Fact: Sometimes cloudy water results from using poor water treatments. We listed our Best Betta Water Conditioner: 5 Aquatic Treatment Options in this article to help you decide properly.

Watch This!

Frequently Asked Questions

Can cloudy aquarium water kill fish?

It depends on the type of cloudy water. For instance, green cloudy water may be a symptom of an underlying problem that may prove deadly in the long run.

Why is my tank cloudy even though there aren’t any fish in it?

Usually, the poorly-washed gravel is the cause of cloudiness. However, if you’re sure you washed the gravel well and it isn’t the cause, it might be the decorations in the tank. You have to wash tank decorations thoroughly before including them as part of your tank setup.

Why is my tank cloudy even though I performed a water change?

This happens because of the debris buildup that occurs when your filter stops and starts. When you turn on your filter, it’ll cause the debris to shoot back into the tank.

Another possible reason for this issue could be the sediment in tap water. However, the water should clear up when left for a couple of days.


Cloudiness in a Betta fish tank is a common issue a lot of fish keepers experience from time to time. It can be caused by several factors which determine how the cloudiness will appear.

Usually, a high level of bacteria in the water may be responsible for the cloudiness, though algal growth and poor water quality may also be responsible.

You can quickly remedy the situation by performing water changes, reducing the number of lights in the room and tank, reducing the amount of fish in the tank, and adding beneficial bacteria, among many other remedies. Meanwhile, refrain from overfeeding your fish, and clean the tank bed regularly to prevent a rise in ammonia and nitrite levels.