5 Reasons A New Tank Is Cloudy With Fish After 1 Day

Last Updated on 2023-10-03

Setting up a new fish tank can be an exciting experience for many. But the aquarium water can turn cloudy pretty soon for a host of different reasons and can leave you wondering what you did wrong.

In fact, when I set up my second tank, the tank was cloudy after 1 day. Fortunately, for me, the tank was only cloudy because the substrate was stirred up too much. But I also ended up researching all the different reasons that a tank ca go cloudy after 1 day!

It turns out there can be many reasons behind this, including a bacterial bloom, residue from the gravel/substrate, an inadequately cleaned tank, bad water conditions, and algae growth.

Read on to discover more about why your new fish tank might be turning cloudy after just 1 day. Happy reading!

Why Is Your Fish Tank Cloudy Without Fish After One Day?

Here are the main reasons that your fish tank may have turned cloudy after one day! However, it’s important to understand one thing.

A cloudy fish tank is completely normal after one day. In most cases, it is caused by the gravel being stirred up when you added it to the tank, however, it can also be a bacterial bloom as the nitrogen cycle begins. This cloudiness will pass after a couple of weeks as the beneficial bacteria in the tank stabilizes.

ReasonSymptomsAdditional Info
Residue from GravelGrey or dark brown waterClears up on its own after a few days
Incorrect pH LevelsAlgae bloom, green waterAlgae thrive in high pH environments
Bacterial Bloom (New Filter)Milky waterOld beneficial bacteria die off, new ones grow
Bacterial Bloom (New Growth)Milky water, ammonia spikeOccurs when water conditions return to normal
Algae GrowthCloudy green waterCaused by direct exposure to sunlight or other light sources

1. Residue From the Gravel

The gravel or the substrate that is used in fish tanks has the potential to turn the water cloudy when it hasn’t been washed properly.

The biggest sign that residue from the gravel is making your tank cloudy is that the water quickly turns grey or dark brown. 

This happened to me when I added aquarium soil to my tank, and it went away on it’s own after a few days!

2. The Water Is Not at the Correct PH Levels

Algae love high pH environments, so the higher the pH in the tank the more likely that you’re going to suffer from an algae bloom in your tank. And of course, if you have an algae bloom in your tank, it will often turn green.

3. Bacterial Bloom Due to New Filter

A bacterial bloom may be the cause of cloudy water in your fish tank if you’ve either used a new filter in the same filtration system or started the existing one after a long time.

This happens because the old beneficial bacteria die off, and the new ones start to grow. This usually turns the tank water cloudy or milky. The water may also turn cloudy if you’re using a new filter medium.

That’s why I always like to keep extra biological media in the filter, so you always have more than enough in case something goes wrong.

4. Bacterial Bloom Due to New Bacteria Growth

The beneficial bacteria in your tank can die for several reasons, including changing water conditions. When these bacteria start growing again, they can turn your tank water milky.

This usually happens when the water conditions have returned to normal. Your tank water turning milky is a sign that the beneficial bacteria have started growing.

It can also be a sign that ammonia in your tank is spiking and the beneficial bacteria is trying to keep up with it.

5. Algae Growth

Algae growth can also be responsible for turning your tank water cloudy. In this case, the tank water becomes cloudy green. Algae growth is usually caused by direct exposure to sunlight or any other source of light.

dirty aquarium with water tree and fish inside wating cleaning

Why Is You Brand-New Fish Tank Cloudy Without Fish?

Now, have a look at some reasons your brand-new fish tank may be cloudy, even when you haven’t put in any fish.

1. The Tank Was Not Properly Cleaned Before Filling It Up

This is one of the most simple reasons your brand-new tank might be cloudy. People who are new to fishkeeping usually make this mistake, which is incredibly easy to avoid. Your new fish tank might have dust and grime on its inside walls, so washing and drying them properly is absolutely necessary before you start filling up the tank with water.

2. The Water Is Not Clean

Another reason your brand-new tank may be cloudy is that it is not filled with clean water. If the water contains impurities, then it can easily make your tank cloudy when you fill it up. This usually happens with tap water. To avoid this mistake, get your source of water tested to determine if it’s clean enough to be used as tank water.

3. Residue From the Gravel/Substrate

This is one reason we’ve discussed previously. But again, if you put gravel in your new tank without first washing it properly, it will certainly make your tank cloudy, as the silt from the substrate spread across the tank.

To make sure this doesn’t happen, wash and clean the gravel thoroughly before putting it into your new tank. Or, if the water is already cloudy, drain it, remove the gravel and wash it properly before replacing it and refilling the tank.

4. Driftwood

Driftwood is a popular choice as a decoration among those setting up their fish tanks., however, you need to treat it properly before you add it to your tank. If you don’t boil your driftwood beforehand, then it will release tannins into the water, turning the water brown.

betta care facebook group

Why Do You Have A Cloudy Green Fish Tank?

There are several possible reasons why a fish tank might appear cloudy and green. Here are some of the most common causes:

Algae Bloom

Algae are microscopic plants that grow in water and can quickly take over a fish tank. When nutrients are abundant, such as excess light or fish waste, algae can bloom and turn the water green.

Poor Water Quality

If a fish tank is not properly maintained, waste and uneaten food can build up and lead to poor water quality. This can cause the water to become cloudy and green as well as potentially harm the fish.

Inadequate Filtration

A filter is necessary to remove waste and debris from the water in a fish tank. If the filter is not sized correctly for the tank or is not working properly, it can result in cloudy and green water.

Overfeeding Fish

When fish are overfed, they produce excess waste and uneaten food, which can decompose and release nutrients into the water. These nutrients can then contribute to the growth of algae, leading to the green appearance of the water.

Too Much Light

Light is necessary for plants to grow in a fish tank, but too much light can also contribute to algae growth. Additionally, if the tank is exposed to direct sunlight, this can also contribute to green water.

New Tank Syndrome

When setting up a new fish tank, it can take several weeks for the water to cycle and become balanced. During this time, it is common for the water to become cloudy and green.


Some medications used to treat fish diseases can cause the water to become cloudy and green as a side effect. This is because some medications contain copper or other chemicals that can react with the water and cause a change in color or appearance.

How Do You Fix Cloudy Water In Your New Tank?

Here are a few ways to fix cloudy water in your brand-new tank.

SolutionApplicationRecommended Product
Test Tank WaterGeneral cloudinessAPI Freshwater Test Kit
Seed the TankBacterial bloomUse biological filter with established beneficial bacteria
Water ReplacementGeneral cloudinessReplace 10-15% of the water
Scrape off AlgaeAlgae build-upUse an algae scraper
Use AlgaecideAlgae bloomFollow product instructions
Use Chemical FiltersTannins from driftwoodChemical filters can remove tannins
WaitBacterial bloomLet the bacterial balance re-establish itself

1. Test the Tank Water

Many problems that make your tank water cloudy can simply be fixed if you test your tank water and clean it accordingly. If you notice the pH is high or the ammonia is high then you know that’s what’s causing the cloudiness. If the cloudy water is caused by residue from gravel, then you just need to let the tank sit for a few days while the cloudiness settles again.

If you’re going to test your water. I’d highly recommend the API Freshwater Test Kit. This is the kit I use and I think it’s so much better than paper test strips. Not only is it more accurate, you get a lot more bang for your buck as well. In fact, I’ve had my test kit for over a year, and I still have plenty of uses left!

API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit, White, Single, Multi-colored
  • Contains one (1) API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit, including 7 bottles of testing solutions, 1 color card and 4 tubes with cap

2. Seed the Tank

To tackle cloudy water one of the best things you can do is seed the tank with a biological filter that has already had beneficial bacteria established in it. Doing so will give your tank a kickstart, which will stop the cloudiness.

3. Replace the Tank Water Regularly

If you notice that the tank water is cloudy, one of the easiest things you can do is simply replace some of the tank water. By replacing 10-15% of the water, you’re going to take lower the ammonia and pH levels in the tank and dilute it even further with clean fresh water.

4. Scrape off the Algae

A build-up of algae is a major cause of cloudy water. Although it doesn’t mean the water is impure, it does make your tank look dirty. You may notice the a green cloudiness in the tank or perhaps the algae has built up on the inside walls of your tank.

Either way scraping of the algae where you can will reduce the amount of cloudiness.

5. Use An Algaecide

You can also use an algaecide when you’re trying to get rid of green cloudiness in your tank. However, just make sure you’re using the product exactly as instructed or you may end up harming your fish and plants.

6. Use Chemical Filters

If your tank water becomes cloudy due to decorations such as driftwood, then using chemical filters might be a good idea to fix that. Chemical filters can remove tannins in the water, however, if the water is extremely brown, then you’ll also need to perform a water change as well.

7. Wait

If your tank is becoming cloudy due to a bacterial bloom, then the best solution might be to just wait and let it clear on its own. Avoid adding chemicals to clear away the cloudiness, as they may end up doing more harm than good. The water will clear after a while, and the bacterial balance will be re-established.

How Long Does It Take For A New Fish Tank To Clear Up?

Watching your new fish tank turn cloudy can be disappointing and worrying. Depending on what is making the water cloudy, the time it takes to clear up can vary greatly. This is because many factors can cause cloudiness.

In many cases, cloudiness in your fish tank is temporary and will clear up on its own after a couple of weeks. If the cloudiness is caused by the growth of beneficial bacteria, however, if the cloudiness is caused by algae, then it won’t clear up unless action is taken.

How To Prevent Cloudy Water In Your New Tank

There are a few things you can do to prevent your tank from becoming cloudy. Keep reading to find out about them.

1. Wash Your New Tank Thoroughly 

This is a no-brainer. When you buy a new tank, make sure to thoroughly wash it in order to remove any dust and grime. Wash both the inside and the outside of the tank and dry it before filling it up with water.

2. Use Clean Water

Using clean water in the first place is important to prevent the water from becoming cloudy later on. Make sure the water you fill your tank up with is clean and doesn’t have any impurities. This can be determined by doing a water test.

3. Wash the Gravel/Substrate

As we mentioned previously, washing your gravel beforehand is important to ensure silt and dust doesn’t end up being blasted into the water when it’s added. So make sure you’re washing gravel thoroughly before adding it to your tank.

4. Avoid Putting the Tank Into Direct Sunlight

Putting your water tank into direct sunlight or near any other light source can allow algae to grow easily since photosynthesis can occur more freely. Algae is a plant, and like all plants, it too grows using photosynthesis. The algae growth, in turn, will turn your water cloudy green in color.

Frequently Asked Questions (FAQs)

Here are some frequently asked questions that people have about why there water is cloudy after one day.

Is Cloudy Water Bad For Fish?

Cloudy water can be bad for fish if it is caused by poor water quality or a lack of oxygen. In general, fish need clean, well-oxygenated water to thrive. Cloudy water can indicate a problem with water quality, which can cause stress, disease, or even death.

Will A Filter Clear Cloudy Water?

Yes, a filter is an essential tool for maintaining a healthy fish tank and can help to clear up cloudy water. A properly sized and functioning filter will remove waste and debris from the water, improving water quality and reducing the amount of cloudiness in the water.

Can Driftwood Make Water Cloudy?

Yes. This is because driftwood can release tannins into the water, which causes water discoloration and make it appear cloudy or brown. While the cloudiness is usually harmless to fish, it can be unsightly and make it difficult to see the fish or other tank inhabitants clearly. 

How Long Will A New Tank Stay Cloudy?

You can expect new tanks to stay cloudy for a couple of weeks. This is generally how long it takes for the beneficial bacteria and the ammonia in your tank to reach a equilibrium, at which point the cloudiness will pass.

How Do I Make My Aquarium Water Crystal Clear?

The best ways to keep your aquarium water crystal clear is by performing water changes regularly, keeping your tank out of direct sunlight, using chemical filtration in your tank, and ensuring no decorations are leeching tannins into the tank.


Although it can be disappointing to see your new fish tank turning cloudy after just 1 day, it is important to diagnose the problem so that you can work on its solution. This guide mentions many different reasons why your tank might be turning cloudy and includes solutions to those problems to help you fix them.

Ultimate Betta Fish Care Guide
About the author

Hey! I'm Nicolas from Iguane Media !

Blogger and Owner of the betta care fish guide
Thanks for reading this blog

I'm an Animal Lover


Enjoy this blog? Please spread the word :)