How To Fix Cloudy Aquarium Water?

When you have an aquarium in your home, you’re recommended to always make sure that the water in your aquarium stays clean and healthy for your fish. Having dirty or cloudy water in your tank can lead to your fish getting sick or developing certain illnesses. In order to best treat the cloudy water situation, you should first find out the reason why your tank has this color water.

Unfortunately the cause of the cloudy water in your fish tank may vary according to the type of tank you have, the size of the tank, the organisms in your tank, and what chemicals or filtration you have to treat the overall condition of the water. Given the complexities of the causes that lead to your tank having cloudy water, you should find out why your tank has cloudy water and then use that information to prevent the water from becoming dirty in the future.

To help you with this process, here is a complete guide that I’ve put together for your convenience. I’ve had cloudy water in my tank plenty of times before, so this article may help as some advice when dealing with the matter. It contains some of the most vital information about properly cleaning your fish tank, some of the reasons that you tank water may be cloudy as well as some additional information about having cloudy tank water in general.

betta fish in an aquarium

Why is Your Water Cloudy?

Since there are so many different factors that can be considered as to why your tank water is dirty or cloudy, the reason really depends on your tank in particular. In order to best understand why your water looks the way that it does, you should observe the specific signs and conditions of your tank. In order to do so, you should consider factors like how your tank water looks, what color it is, how hazy it is, how it smells, and various other factors.

I’ve compiled together some common conditions that you may observe about your tank that can cause your tank water to become dirty or hazy, and I’ve also created a guide on what you can do as solution for each cause.

White or Gray Water

Gravel residue

If your aquarium water shows a white or gray haze, then it could be caused by residue from the gravel in your tank. This is usually the case directly after you’ve filled your tank with water, since the water pouring into the tank causes the dirt and debris from the gravel substrate to flow up into the water.


In order to clear the cloudy aquarium water from your tank if it’s from residue in gravel, you should drain the whole tank and refill it with clean water after you’ve rinsed the gravel thoroughly. You can prevent this problem from occurring in the future by vacuuming your gravel often and making sure that the gravel and other material substrates stay clean. Not only that, but you can also prevent this from occurring by ensuring that you rinse your gravel thoroughly before you place it in your tank during every water change (1).

Bacterial Bloom

Bacterial bloom occurs when there is a buildup of beneficial bacteria. Beneficial bacteria are initially present in your tank water in order to balance the amount of ammonia in your tank, but having an excess of the beneficial bacteria can cause your tank water to look cloudy. The excess amount of free floating bacteria won’t exactly harm the fish in your aquarium, but it can make your fish’s visibility more difficult.

Bacterial bloom usually occurs within the beginning stages of the tank cycling process, since the balances in the water won’t be set in place yet.


To make tank water less cloudy due to bacterial bloom, it’s best to leave the water alone. Many people think that immediately changing the water when it’s cloudy is the best solution, but sometimes the problem can go away on its own. If your fish don’t seem to be breathing at the surface of the water or bothered by the bacteria in the water, then you should let the water sit in the tank until the bacteria settle and clear the water up.

If your fish are bothered by the bacteria, then you should conduct a water change of about half of the tank water to remove some of the bacteria from the tank (2).

Dissolved constituents

Cloudy water represented in more of a white or gray color could also be a high amount of dissolved constituents. More specifically, if you have a new aquarium with cloudy water, the cloudiness is probably caused by an excess of phosphates, silicates, or other heavy metals in your tank. You should test the pH levels of the water, and the cloudiness is caused by dissolved constituents if the pH levels are high.


You should consider putting water conditioner in your aquarium if the pH levels are too high due to an excess in phosphates, silicates, or other heavy metals. You may also benefit from placing Reverse Osmosis water into the tank, since it will help to clear up the cloudiness.

Green Water

Too much light

Your tank water may turn a green color if you have too much light shining in your tank for too long throughout the day. Having too much light causes the plants in your aquarium to grow too fast, and it can even create algae growth that takes over your aquarium.


To prevent your plants from growing too quickly or algae growing, you can reduce the amount of time that your tank is exposed to light. This may also mean that you have to change the location of your tank, since natural sunlight from the window may be causing the growth.

Nitrates or Phosphates

Having an excess amount of nitrates or phosphates in your tank water can also cause a green haze to occur. The level of nitrates in your water can occur because of too much fish waste accumulating over time, and phosphates can result from decaying matter or from the condition of the water itself.

Nitrates and phosphates are responsible for fighting off and reducing the amount of algae that grows in your tank. But certain circumstances can lead to an over-abundance of nitrates, phosphates, and other nutrients in your aquarium water, thus creating a cloudy green haze in the water.


To limit the amount of nitrates in your tank water, you should change your tank water and make sure that your aquarium filter is working effectively, since the filter is technically responsible for removing nitrates from your water. To remove the phosphates from your water, you can add a phosphate remover to your water to limit the level os phosphates (1).


Phytoplankton is classified as a certain type of algae that can cause your water to turn green when it takes over too much of your tank. Phytoplankton won’t harm your fish when there happens to be an over-abundance of the algae, but it can make your tank look dirty and unhealthy. Sometimes there are severe cases where you won’t even be able to see your fish or other elements in the water.

Having an overgrowth of phytoplankton in your tank can be caused by a few different factors, including having a dirty filter, not cleaning your tank water on time, having too much light, not having enough CO2 in your tank, and having an imbalance of fertilizer in your water.


In order to remove an overgrowth of phytoplankton in your fish tank, you should install a UV sterilizer or a stronger filter media. Some filters have a media that’s too large, so installing a filter with a finer media can help remove the excess phytoplankton effectively.

Yellow or Brown Water


If your cloudy water has a yellow or brown tint to it, your tank may have driftwood in it. Driftwood are small clumps of particles from leaves, wood, and seed pods. The brownish color of the particles that these substances turn your water is called tannin, and some people even prefer to have their aquarium this color because of the beauty when it’s done properly.

You typically have this color occur because of placing certain logs or plants that release their leaves into the water.


You can remove the brownish color and tannin from your aquarium by installing a carbon filter in your tank. Carbon filters are able to filter out the brown or yellow color. You can also prevent this from occurring in the future by pre-soaking the logs before placing them into the water (3).

Consequences of Cloudy Aquarium Water

Depending on the certain reason that your aquarium water is cloudy, not taking care of it properly can result in even more severe problems. For instance, having too many chemicals of a certain kind or having imbalanced pH levels can result in your fish developing a disease or even death.

Not only that, but having too much sunlight exposed to your tank can result in algae growth that can kill your fish and overcome your tank if the algae isn’t contained. Given that, you should treat each certain problem the right way to prevent any future problems from occurring.

How to Prevent Cloudy Water

Don’t overfeed your fish

Overfeeding the fish in your tank can lead to cloudy water, since your fish won’t eat the leftover excess food. Instead, they’ll leave it sitting in the water, which will then decay in the tank and can cause problems if it’s not taken care of properly. Only feed your fish the right amount of food that they’ll all consume. And if there’s any leftover, you should remove it after you’re done with the fish.

No overcrowding your tank with fish

Putting too many fish in your tank can also cause the water to become cloudy, since there will be an excess of fish waste in the tank. Regardless of how strong your filter is, it won’t be able to remove all of the fish waste in the tank if it’s overcrowded. Even more than that, having excess fish waste can lead to an excess in the amount of nitrites and ammonia as well, causing more problems. Having too many fish in your tank can be unhealthy and unsanitary as it is, so it’s highly recommended that you avoid it.

To find out how many fish you should have in your tank depends on the size of your tank as well as the size of the fish and how many decorations you have in the aquarium. But you can find the recommended limits on the manuals for your aquariums.

Test your water often

In order to prevent your aquarium from experiencing cloudy water in the future, you should keep up on testing the water in the fish tank. Testing the water can help you know the certain levels of chemicals and other helpful elements in the tank, like ammonia, nitrates, nitrites, and other elements. Make sure that the pH levels as well as the chemicals in your tank are always within healthy limits (4).


Overall, having cloudy water in your aquarium not only has the potential of causing problems for the tank as well as the fish in the tank, but it’s merely annoying when you can’t see all of your fish and interact with them. Likewise, your fish likely have problems seeing in the water as well, so it can irritate and stress out the organisms that are living in the tank.

Given that, you should find out why you have cloudy water in your aquarium and then accommodate for that by solving the problem. Whether you have to simply change the aquarium water or purchase a certain product or water conditioner, you should keep up with cleaning your tank water as well as providing your aquarium with adequate filtration processes in order to prevent cloudy water from developing in the future.

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